{"url":"https://www.servnetuk.com/research/uk-large-site-electricity-data-centres-2026","slug":"uk-large-site-electricity-data-centres-2026","study":"One of 325 local authorities has an average half-hourly meter as big as it was in 2013: Slough","question":"Great Britain's large-site electricity peaked in 2018 and has fallen since, while the meter base carrying it has grown sharply. Which local authorities have not followed, once the settlement-migration artefact that distorts every naive comparison is measured and a window between the two settlement breaks is tested alongside, and how much of the difference is data centres when they are measured against a large-site denominator rather than the all-electricity one that includes homes?","publisher":"Servnet","built":"2026-09-20","builder":"Servnet Research, scripts/research/uk-large-site-electricity-data-centres-2026/analyse.py","data_as_at":"2026-09-20","as_at_line":"Computed 2026-09-20 from DESNZ statistical releases downloaded 2026-09-20T06:48Z. Half-hourly and subnational data are the 18 December 2025 editions; the data-centre tables are the 30 June 2026 edition.","licence":{"source_data":"Open Government Licence v3.0","source_data_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","attribution_required":"Contains public sector information licensed under the Open Government Licence v3.0.","derived_work":"Creative Commons Attribution 4.0 International (CC BY 4.0)","derived_work_url":"https://creativecommons.org/licenses/by/4.0/","derived_attribution":"Servnet, One of 325 local authorities has an average half-hourly meter as big as it was in 2013: Slough, https://www.servnetuk.com/research/uk-large-site-electricity-data-centres-2026","parliamentary_licence":"Open Parliament Licence v3.0","parliamentary_licence_url":"https://www.parliament.uk/site-information/copyright-parliament/open-parliament-licence/","parliamentary_attribution_required":"Contains Parliamentary information licensed under the Open Parliament Licence v3.0.","third_party_rights":"One source, the House of Commons Library briefing, is Parliamentary copyright reused under the Open Parliament Licence v3.0, which requires this statement to be carried: 'Contains Parliamentary information licensed under the Open Parliament Licence v3.0.' Utility Bidder and LBC are cited as prior art and coverage under fair quotation, with acknowledgement; no data from either is reused.","personal_data":"The published dataset contains no personal data. Every row is a local authority. No individual is named in any output of this study, and the redaction step that stripped the names in the source documents holds them as salted hashes so no name is retained in the repository either."},"population":{"n":378,"unit":"local authority","definition":"Every local authority in Great Britain that appears in the half-hourly rows of the DESNZ MSOA non-domestic electricity workbook in any year from 2010 to 2024, identified on the reconciled basis. This is a population, not a sample.","matched_panels":{"intensity_base_2013_to_2024":325,"present_in_every_year_2015_to_2024":350,"present_in_every_year_2010_to_2024":342,"clean_window_base_2019_to_2023":349,"concentration_base_2019_to_2023":350},"rows_per_year":{"2010":370,"2011":371,"2012":371,"2013":371,"2014":371,"2015":350,"2016":350,"2017":350,"2018":350,"2019":350,"2020":350,"2021":350,"2022":350,"2023":350,"2024":350},"unallocated":{"rows":15,"note":"One per year, held out of every total and reported separately."}},"preRegisteredMetrics":[{"id":"intensity-parity-count","statement":"Exactly one local authority in the intensity base had an average half-hourly meter drawing at least as much electricity in 2024 as in 2013: Slough.","margin_note":"Read the count and the margin together. The count is not close: second place is Hart at 0.6222, so no other authority is anywhere near parity. Slough's own position is close: it clears parity by 0.08 per cent, or 0.0014 GWh per meter. DESNZ revises these years at every annual publication (see the revisions caveat), and a downward revision of a tenth of one per cent to Slough's 2024 mean would turn 'exactly one' into 'none'. The median finding, and the 2019 to 2023 test, do not turn on anything that fine.","value":1,"unit":"local authorities","n":325,"denominator":325,"denominator_label":"local authorities with more than 100 half-hourly meters in 2013 that are also present in 2024, on the reconciled identity basis","how_to_recompute":"In the published CSV: count rows where in_intensity_base_reconciled = 1 and intensity_ratio_2013_2024 >= 1.","robustness":{"published_name_basis":{"n":303,"value":1},"published_code_basis":{"n":323,"value":1}},"brief_expected_n":303,"n_actually_used":325,"why_n_differs_from_the_brief":"303 is the number produced by matching on the published name with no normalisation. DESNZ writes the twenty-two Welsh authorities monolingually in 2013 and bilingually in 2024 ('Cardiff' against 'Cardiff / Caerdydd'), so literal name matching drops all twenty-two for a spelling reason. Matching on the published code drops Barnsley and Sheffield instead, which were recoded in 2016. The reconciled basis keeps all of them and gives n=325. The finding is the same on all three: exactly one authority at or above parity, and a median of 0.29."},{"id":"intensity-median","statement":"The median local authority's average half-hourly meter drew 29 per cent as much electricity in 2024 as in 2013.","value":0.2914,"unit":"ratio of 2024 mean kWh per half-hourly meter to 2013","n":325,"denominator":"the same local authority's 2013 mean kWh per half-hourly meter","denominator_label":"each authority is its own denominator; the statistic is the median of those ratios","how_to_recompute":"Median of intensity_ratio_2013_2024 over rows with in_intensity_base_reconciled = 1.","robustness":{"published_name_basis":0.2901,"published_code_basis":0.2906},"reading_note":"This ratio is not a measure of demand. Settlement migration moved smaller sites into the half-hourly category, which lowers the average wherever it happened, and it happened almost everywhere. Great Britain's own mean fell from 1.0435 to 0.3140 GWh per half-hourly meter over the same period, a ratio of 0.301, so the median authority is close to simply tracking the national reclassification."},{"id":"slough-intensity","statement":"Slough's average half-hourly meter drew 1.8878 GWh in 2013 and 1.8892 GWh in 2024.","value_from_gwh":1.8878,"value_to_gwh":1.8892,"ratio":1.0008,"n":1,"denominator":"Slough's own 2013 mean, and its own half-hourly meter count in each year","denominator_label":"mean kWh per half-hourly meter = total half-hourly kWh divided by the half-hourly meter count, as published by DESNZ; 383 meters in 2013 and 918 in 2024","how_to_recompute":"The Slough row of the published CSV: hh_mean_gwh_per_meter_2013 and hh_mean_gwh_per_meter_2024.","margin_note":"The gap between the two figures is 0.0014 GWh per meter, 0.08 per cent. This is a thin margin over parity and it should be read next to the revisions caveat: DESNZ revises 2015 onwards at every annual publication, and a later edition will not reproduce these figures exactly.","caveat":"2024 figure. A large reclassification break appears in the 2024 half-hourly data: half-hourly meters rose 23.6 per cent in one year, or 23.4 per cent with the Unallocated row left out, while total non-domestic meters rose 1.3 per cent, and 344 of the 349 local authorities with at least 100 half-hourly meters in 2023 gained more than 5 per cent. No explanation for it appears in the documents read here. It is not Market-wide Half Hourly Settlement: Ofgem's CR055 decision puts MHHS meter migration between late October 2025 and May 2027, after this data year. Any 2024 figure on this page sits on a meter base that earlier years do not share."},{"id":"clean-window-parity","statement":"Over 2019 to 2023, a window that contains neither documented settlement break, though P322 continued to move meters across it, 6 of 349 local authorities had an average half-hourly meter at or above its 2019 level, and Slough was the highest at 1.414.","value":6,"n":349,"denominator":349,"denominator_label":"local authorities with more than 100 half-hourly meters in 2019 that are present in 2023","how_to_recompute":"Count rows where intensity_ratio_2019_2023_clean_window >= 1.","why_it_matters":"It is the same test with both documented reclassification events outside the window, so it does not depend on any judgement about what P272 or the 2024 break did. It is quieter than 2013 to 2024 but it is not perfectly still: half-hourly meters in Great Britain still rose 8.5 per cent across it, because P322 keeps moving meters as businesses change contract. This test gives 6 authorities at or above parity where the 2013 to 2024 test gives one, which is consistent with the longer window carrying far more reclassification rather than less real growth."},{"id":"concentration-direction","statement":"Between 2019 and 2023, 326 of 350 local authorities used less half-hourly electricity and 24 used more.","value_down":326,"value_up":24,"n":350,"denominator":350,"denominator_label":"every local authority in the half-hourly panel in both 2019 and 2023","how_to_recompute":"Count hh_direction_2019_2023 in the published CSV."},{"id":"concentration-top10","statement":"The ten largest risers account for 94.6 per cent of all the growth in half-hourly electricity between 2019 and 2023.","value_pct":94.6,"n":24,"denominator":1093.9,"denominator_label":"the sum of the increases of the 24 local authorities that used more, 1,093.9 GWh; falls are not netted off","how_to_recompute":"Sum hh_gwh_change_2019_2023 over the ten largest positive values, divide by the sum of all positive values."},{"id":"migration-immune-direction","statement":"On the all-non-domestic series, which a meter cannot move between by being reclassified, 337 of 350 local authorities used less between 2019 and 2023 and 13 used more.","value_down":337,"value_up":13,"n":350,"denominator":350,"denominator_label":"every local authority in the subnational panel in both 2019 and 2023","how_to_recompute":"Count all_non_domestic_direction_2019_2023 in the published CSV."},{"id":"migration-immune-top10","statement":"On that migration-immune series the ten largest risers account for 99.1 per cent of all growth.","value_pct":99.13,"n":13,"denominator":941.7,"denominator_label":"the sum of the increases of the 13 local authorities that used more, 941.7 GWh; falls are not netted off","how_to_recompute":"Sum all_non_domestic_gwh_change_2019_2023 over the ten largest positive values, divide by the sum of all positive values.","small_n_note":"Only 13 local authorities used more on this series. That is above the ten-case floor this study sets for reporting a percentage, but it is a small group and the percentage should be read with that in mind."},{"id":"top10-set-identity","statement":"The ten largest risers are the same ten local authorities on both series, in a slightly different order.","value":true,"same_order":false,"n":10,"denominator":"the top ten of each of the two rankings","denominator_label":"membership comparison, not a percentage","how_to_recompute":"Compare hh_riser_rank_2019_2023 <= 10 with all_non_domestic_riser_rank_2019_2023 <= 10."},{"id":"dc-denominator-gb","statement":"Data centres were 3.67 per cent of Great Britain's large-site electricity in 2024 — an approximation, an all-meter numerator over a half-hourly denominator — against the 1.79 per cent of all electricity DESNZ publishes.","value_pct":3.67,"n":1,"denominator":121.522,"denominator_label":"half-hourly (large-site) electricity in the same area in 2024, 121.5220 TWh","published_comparison_pct":1.79,"published_denominator_label":"all electricity taken from the grid, domestic and non-domestic","how_to_recompute":"4.4595 TWh divided by 121.5220 TWh. The denominator is the sum of hh_gwh_2024 over all rows of the published CSV, divided by 1,000, which excludes the Unallocated row.","label":"Approximation: an all-meter numerator over a half-hourly denominator, covering slightly different twelve-month periods.","caveat":"2024 figure. A large reclassification break appears in the 2024 half-hourly data: half-hourly meters rose 23.6 per cent in one year, or 23.4 per cent with the Unallocated row left out, while total non-domestic meters rose 1.3 per cent, and 344 of the 349 local authorities with at least 100 half-hourly meters in 2023 gained more than 5 per cent. No explanation for it appears in the documents read here. It is not Market-wide Half Hourly Settlement: Ofgem's CR055 decision puts MHHS meter migration between late October 2025 and May 2027, after this data year. Any 2024 figure on this page sits on a meter base that earlier years do not share."},{"id":"dc-denominator-slough","statement":"In Slough, data centres were 74.6 per cent of large-site electricity in 2024 — an approximation, an all-meter numerator over a half-hourly denominator — against the 65 per cent of all electricity DESNZ publishes.","value_pct":74.58,"n":1,"denominator":1.7343,"denominator_label":"half-hourly (large-site) electricity in the same area in 2024, 1.7343 TWh","published_comparison_pct":65.16,"published_denominator_label":"all electricity taken from the grid, domestic and non-domestic","how_to_recompute":"The Slough row: data_centre_twh_2024 divided by hh_gwh_2024 / 1,000.","label":"Approximation: an all-meter numerator over a half-hourly denominator, covering slightly different twelve-month periods.","caveat":"2024 figure. A large reclassification break appears in the 2024 half-hourly data: half-hourly meters rose 23.6 per cent in one year, or 23.4 per cent with the Unallocated row left out, while total non-domestic meters rose 1.3 per cent, and 344 of the 349 local authorities with at least 100 half-hourly meters in 2023 gained more than 5 per cent. No explanation for it appears in the documents read here. It is not Market-wide Half Hourly Settlement: Ofgem's CR055 decision puts MHHS meter migration between late October 2025 and May 2027, after this data year. Any 2024 figure on this page sits on a meter base that earlier years do not share."}],"page":{"title":"One of 325 local authorities has an average half-hourly meter as big as it was in 2013: Slough","standfirst":"Great Britain's large-site electricity peaked in 2018 and is 11.1 per cent lower in 2024, while the number of half-hourly meters carrying it has risen 219 per cent since 2013, so the average half-hourly meter is a fraction of the size it was. Much of that fall is settlement reclassification rather than demand. Measure each local authority against its own 2013 average, which reduces that distortion without removing it, and one of the 325 authorities with a large-site base in 2013 is left level: Slough, by 0.08 per cent. Over 2019 to 2023, a window between the two documented settlement breaks — though half-hourly meters still rose 8.5 per cent across it — 6 of 349 authorities are level or above.","as_at_line":"Computed 2026-09-20 from DESNZ statistical releases downloaded 2026-09-20T06:48Z. Half-hourly and subnational data are the 18 December 2025 editions; the data-centre tables are the 30 June 2026 edition.","wording_rules":["Say which denominator a percentage uses, every time. Two denominators are in play: all electricity from the grid including homes, and large-site (half-hourly) electricity.","Never add a half-hourly figure to a non-half-hourly one. Half-hourly covers January to December; non-half-hourly covers February to January.","Every 2024 figure carries the reclassification-break caveat. Do not attribute the 2024 break to MHHS: MHHS migration runs from late October 2025 to May 2027.","Say 'the average half-hourly meter', not 'the average site'. A meter is not a building and not a business.","Do not claim to be first to notice that Slough's electricity is rising or that almost every local authority is falling. Both have been published before.","Credit Utility Bidder's February 2026 league table in the opening, and state plainly that we have not independently checked their figures.","Where the data-centre overlay appears, carry the approximation label with it.","Report n for every cut. Do not report a percentage on fewer than ten cases without saying so."],"headlines":[{"metric":"Local authorities whose average large-site meter is as big as it was in 2013","value":"1 of 325","detail":"Slough, at a ratio of 1.0008. It clears parity by 0.08 per cent, or 0.0014 GWh per meter, so its own position is thin, and a downward revision of a tenth of one per cent to Slough's 2024 mean would make it none. What is not thin is the gap to second place: Hart, at 0.6222. See the revisions caveat","denominator":"local authorities with more than 100 half-hourly meters in 2013 and present in 2024","source":"DESNZ MSOA non-domestic electricity workbook 2010-2024"},{"metric":"The same test over 2019 to 2023, between the two documented settlement breaks (half-hourly meters still rose 8.5 per cent across it)","value":"6 of 349","detail":"Those 6 are at or above their 2019 average per meter, Slough highest at 1.4135; the 2013 to 2024 test gives one, which is consistent with the longer window carrying far more reclassification rather than less real growth","denominator":"local authorities with more than 100 half-hourly meters in 2019 and present in 2023","source":"DESNZ MSOA non-domestic electricity workbook 2010-2024"},{"metric":"The median local authority's average large-site meter, 2024 against 2013","value":"29%","detail":"interquartile range 0.25 to 0.34","denominator":"each authority's own 2013 mean kWh per half-hourly meter, n=325","source":"DESNZ MSOA non-domestic electricity workbook 2010-2024"},{"metric":"Local authorities using less large-site electricity, 2019 to 2023","value":"326 of 350","detail":"24 used more","denominator":"every local authority in the half-hourly panel in both years","source":"DESNZ MSOA non-domestic electricity workbook 2010-2024"},{"metric":"Share of all large-site growth taken by the ten largest risers","value":"94.6%","detail":"of 1,093.9 GWh of increases, falls not netted off; 99.1% of 941.7 GWh on the migration-immune series, over only 13 rising authorities","denominator":"the sum of the increases of the 24 local authorities that used more, 1,093.9 GWh; falls are not netted off","source":"DESNZ MSOA workbook and DESNZ subnational electricity statistics"},{"metric":"Data centres as a share of Great Britain's large-site electricity, 2024","value":"3.67%","detail":"against 1.79% of all electricity, the figure DESNZ publishes. An approximation: an all-meter numerator over a half-hourly denominator","denominator":"half-hourly (large-site) electricity in the same area in 2024, 121.5220 TWh","source":"DESNZ Energy Trends June 2026 data-centre tables over the DESNZ MSOA half-hourly panel"},{"metric":"Data centres as a share of Slough's large-site electricity, 2024","value":"74.6%","detail":"against 65% of all electricity in Slough, the figure DESNZ publishes. An approximation: an all-meter numerator over a half-hourly denominator","denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7343 TWh","source":"DESNZ Energy Trends June 2026 data-centre tables over the DESNZ MSOA half-hourly panel"}],"sections":[{"id":"prior-art","order":1,"heading":"What was already known","body":"Two things in this study have been published before, and both should be credited before anything new is claimed. DESNZ itself publishes the finding that data centres accounted for around two-thirds (65 per cent) of the electricity taken from the grid in Slough in 2024, in its June 2026 Energy Trends special feature. Utility Bidder published a local authority league table with a per-meter intensity measure in February 2026, comparing 2020 with 2024 on a per non-domestic meter basis, and put Slough at the top of it. That description of their work is not checked: a request with our identifying user agent returned HTTP 403 and we did not disguise it or retry, so what we know of their page came back through a general-purpose fetch tool instead. No figure of theirs is reproduced here and no data from them is used.","what_this_adds":["A different measure on a different base: consumption per half-hourly (large-site) meter, not per non-domestic meter, over 2013 to 2024 rather than 2020 to 2024, on the set of authorities that had a large-site base in 2013.","The settlement-migration artefact measured rather than assumed away, with a second test over a window that contains neither of the two documented settlement breaks.","Every riser checked against the all-non-domestic series, which reclassification cannot move.","The data-centre overlay recomputed against a large-site denominator instead of the all-electricity denominator, homes included, that DESNZ uses."],"not_claimed":"We do not claim to be first to notice that Slough's electricity consumption is rising, or that almost every local authority's is falling."},{"id":"the-artefact","order":2,"heading":"The artefact that breaks the naive comparison","body":"DESNZ classifies a meter as half-hourly or not by its settlement profile class, not by what the site does. Two changes moved large numbers of meters across that line without changing a single unit of electricity used. The first is documented: BSC modification P272, with P322 alongside it, moved profile classes 5 to 8 that had an advanced meter installed into half-hourly settlement between November 2015 and April 2017, and it is the larger of the two by a wide margin — half-hourly meter numbers more than doubled, rising 108.6 per cent in those two years. A second break appears in 2024. It is smaller, at 23.41 per cent in one year, but it is the largest single-year jump outside the P272 window, and no explanation for it appears in the documents we read. The printed national series carries a third movement as well, before that window: half-hourly meters rise from 121,327 in 2013 to 145,104 in 2014 and fall back to 127,478 in 2015, across the change of geography basis. It is smaller than either break, no explanation for it appears in the documents we read either, and no finding here is measured on it — but the 2013 to 2024 comparison runs across it, which is one more reason the 2019 to 2023 window is reported alongside.","findings":{"gb_series":[{"year":2010,"local_authorities":370,"hh_meters":112514,"hh_twh":126.177,"mean_gwh_per_hh_meter":1.1214,"unallocated_hh_meters":4890,"unallocated_hh_twh":5.8181,"geography_basis":"2011 Census geographies"},{"year":2011,"local_authorities":371,"hh_meters":109195,"hh_twh":117.593,"mean_gwh_per_hh_meter":1.0769,"unallocated_hh_meters":4061,"unallocated_hh_twh":5.5641,"geography_basis":"2011 Census geographies"},{"year":2012,"local_authorities":371,"hh_meters":118095,"hh_twh":124.145,"mean_gwh_per_hh_meter":1.0512,"unallocated_hh_meters":4486,"unallocated_hh_twh":5.8456,"geography_basis":"2011 Census geographies"},{"year":2013,"local_authorities":371,"hh_meters":121327,"hh_twh":126.608,"mean_gwh_per_hh_meter":1.0435,"unallocated_hh_meters":4437,"unallocated_hh_twh":5.8954,"geography_basis":"2011 Census geographies"},{"year":2014,"local_authorities":371,"hh_meters":145104,"hh_twh":125.63,"mean_gwh_per_hh_meter":0.8658,"unallocated_hh_meters":4973,"unallocated_hh_twh":5.7937,"geography_basis":"2011 Census geographies"},{"year":2015,"local_authorities":350,"hh_meters":127478,"hh_twh":126.402,"mean_gwh_per_hh_meter":0.9916,"unallocated_hh_meters":1700,"unallocated_hh_twh":2.713,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2016,"local_authorities":350,"hh_meters":211531,"hh_twh":128.331,"mean_gwh_per_hh_meter":0.6067,"unallocated_hh_meters":2316,"unallocated_hh_twh":2.8364,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2017,"local_authorities":350,"hh_meters":265975,"hh_twh":135.471,"mean_gwh_per_hh_meter":0.5093,"unallocated_hh_meters":2695,"unallocated_hh_twh":2.8858,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2018,"local_authorities":350,"hh_meters":280754,"hh_twh":136.747,"mean_gwh_per_hh_meter":0.4871,"unallocated_hh_meters":2705,"unallocated_hh_twh":2.8454,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2019,"local_authorities":350,"hh_meters":288854,"hh_twh":134.204,"mean_gwh_per_hh_meter":0.4646,"unallocated_hh_meters":2692,"unallocated_hh_twh":2.7073,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2020,"local_authorities":350,"hh_meters":289457,"hh_twh":118.968,"mean_gwh_per_hh_meter":0.411,"unallocated_hh_meters":2697,"unallocated_hh_twh":2.4237,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2021,"local_authorities":350,"hh_meters":292431,"hh_twh":122.904,"mean_gwh_per_hh_meter":0.4203,"unallocated_hh_meters":2786,"unallocated_hh_twh":2.6852,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2022,"local_authorities":350,"hh_meters":314571,"hh_twh":124.246,"mean_gwh_per_hh_meter":0.395,"unallocated_hh_meters":2829,"unallocated_hh_twh":2.6763,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2023,"local_authorities":350,"hh_meters":313550,"hh_twh":121.38,"mean_gwh_per_hh_meter":0.3871,"unallocated_hh_meters":2835,"unallocated_hh_twh":2.6307,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2024,"local_authorities":350,"hh_meters":386961,"hh_twh":121.522,"mean_gwh_per_hh_meter":0.314,"unallocated_hh_meters":4132,"unallocated_hh_twh":2.6826,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"}],"p272_window":{"from_year":2015,"to_year":2017,"hh_meters_from":127478,"hh_meters_to":265975,"hh_meters_change":138497,"mean_gwh_per_meter_from":0.9916,"mean_gwh_per_meter_to":0.5093,"n_local_authorities_tested":337,"median_per_meter_ratio":0.5272,"n_at_or_above_parity":0,"reading":"Average large-site load appeared to fall by nearly half in two years. Nothing in the country's electricity use did that. Reclassification did."},"break_2024":{"from_year":2023,"to_year":2024,"hh_meters_from":313550,"hh_meters_to":386961,"hh_meters_change_pct":23.41,"denominator_for_that_percentage":"half-hourly meters in Great Britain in 2023, excluding the Unallocated row","hh_meters_change_pct_including_unallocated":23.61,"n_local_authorities_tested":349,"median_per_meter_ratio":0.7941,"n_at_or_above_parity":2,"cause":"No explanation for it appears in the 2024 summary report or on the cover sheets of the three workbooks used here; we did not obtain the current subnational energy statistics methodology note, which the MSOA cover sheet points readers to for discrepancies of this kind, so it may be explained somewhere we did not read. What can be ruled out is Market-wide Half Hourly Settlement: Ofgem's CR055 decision of 29 November 2024 puts MHHS meter migration between late October 2025 and May 2027, entirely after this data year."},"slough_meter_counts":[{"year":2010,"hh_meters":347},{"year":2011,"hh_meters":356},{"year":2012,"hh_meters":365},{"year":2013,"hh_meters":383},{"year":2014,"hh_meters":460},{"year":2015,"hh_meters":401},{"year":2016,"hh_meters":643},{"year":2017,"hh_meters":793},{"year":2018,"hh_meters":817},{"year":2019,"hh_meters":822},{"year":2020,"hh_meters":822},{"year":2021,"hh_meters":830},{"year":2022,"hh_meters":856},{"year":2023,"hh_meters":841},{"year":2024,"hh_meters":918}],"why_per_meter":"Because a local authority total moves when meters are reclassified into it and a per-meter mean is far less sensitive to that. Slough's half-hourly meter count went from 383 in 2013 to 918 in 2024. Those are not 535 new sites.","what_per_meter_does_not_fix":"Migration still drags the per-meter mean down wherever it happened, because the meters that moved in were smaller than the ones already there. That is why the median ratio is 0.29 rather than something near 1, and why the interesting question is which authority stayed at 1 despite it. DESNZ makes the same point about its own statistics: percentage changes in total consumption stay reliable, but meter counts and per-meter means can be distorted by meters crossing a classification threshold."}},{"id":"intensity-test","order":3,"heading":"The large-site intensity test","body":"Take every local authority that had a meaningful large-site base in 2013, defined as more than 100 half-hourly meters, and compare the average electricity per half-hourly meter in 2024 with 2013. The test is a ratio of published means, so each authority is its own denominator.","findings":{"primary":{"basis":"reconciled identity","matching_rule":"Reconciled identity: the published name with the Welsh bilingual second form removed, which is identical in result to matching on the ONS code with the two 2016 recodes applied (Barnsley E08000016 to E08000038, Sheffield E08000019 to E08000039). Both give the same set and the same figures.","n_eligible_2013":350,"n":325,"n_dropped":25,"why_dropped":"Local government reorganisation. Authorities that were merged or replaced between the 2011 Census geography used to 2014 and the 2021 and 2022 geographies used from 2015 have no counterpart in 2024.","median_ratio":0.2914,"q1_ratio":0.2488,"q3_ratio":0.3394,"min_ratio":0.1511,"max_ratio":1.0008,"n_at_or_above_parity":1,"at_or_above_parity":[{"name":"Slough","code":"E06000039","ratio":1.0008}],"top_20":[{"rank":1,"name":"Slough","code":"E06000039","mean_gwh_per_meter_2013":1.8878,"mean_gwh_per_meter_2024":1.8892,"ratio":1.0008,"hh_meters_2013":383,"hh_meters_2024":918},{"rank":2,"name":"Hart","code":"E07000089","mean_gwh_per_meter_2013":0.6385,"mean_gwh_per_meter_2024":0.3973,"ratio":0.6222,"hh_meters_2013":170,"hh_meters_2024":627},{"rank":3,"name":"Hillingdon","code":"E09000017","mean_gwh_per_meter_2013":1.5137,"mean_gwh_per_meter_2024":0.8595,"ratio":0.5678,"hh_meters_2013":601,"hh_meters_2024":1627},{"rank":4,"name":"Tower Hamlets","code":"E09000030","mean_gwh_per_meter_2013":1.0414,"mean_gwh_per_meter_2024":0.5822,"ratio":0.5591,"hh_meters_2013":1991,"hh_meters_2024":2978},{"rank":5,"name":"Dacorum","code":"E07000096","mean_gwh_per_meter_2013":0.8381,"mean_gwh_per_meter_2024":0.4657,"ratio":0.5557,"hh_meters_2013":270,"hh_meters_2024":913},{"rank":6,"name":"City of London","code":"E09000001","mean_gwh_per_meter_2013":1.3228,"mean_gwh_per_meter_2024":0.6993,"ratio":0.5286,"hh_meters_2013":1647,"hh_meters_2024":2083},{"rank":7,"name":"Argyll and Bute","code":"S12000035","mean_gwh_per_meter_2013":0.4192,"mean_gwh_per_meter_2024":0.2184,"ratio":0.521,"hh_meters_2013":255,"hh_meters_2024":628},{"rank":8,"name":"Westminster","code":"E09000033","mean_gwh_per_meter_2013":0.7899,"mean_gwh_per_meter_2024":0.4023,"ratio":0.5093,"hh_meters_2013":3172,"hh_meters_2024":5683},{"rank":9,"name":"Camden","code":"E09000007","mean_gwh_per_meter_2013":0.8274,"mean_gwh_per_meter_2024":0.3874,"ratio":0.4682,"hh_meters_2013":1187,"hh_meters_2024":2326},{"rank":10,"name":"Greenwich","code":"E09000011","mean_gwh_per_meter_2013":0.5809,"mean_gwh_per_meter_2024":0.2659,"ratio":0.4578,"hh_meters_2013":485,"hh_meters_2024":1238},{"rank":11,"name":"North Warwickshire","code":"E07000218","mean_gwh_per_meter_2013":1.5528,"mean_gwh_per_meter_2024":0.6984,"ratio":0.4498,"hh_meters_2013":212,"hh_meters_2024":544},{"rank":12,"name":"Derby","code":"E06000015","mean_gwh_per_meter_2013":0.8275,"mean_gwh_per_meter_2024":0.3694,"ratio":0.4464,"hh_meters_2013":500,"hh_meters_2024":1331},{"rank":13,"name":"East Lindsey","code":"E07000137","mean_gwh_per_meter_2013":0.7228,"mean_gwh_per_meter_2024":0.3211,"ratio":0.4443,"hh_meters_2013":329,"hh_meters_2024":972},{"rank":14,"name":"Newport / Casnewydd","code":"W06000022","mean_gwh_per_meter_2013":1.8494,"mean_gwh_per_meter_2024":0.8198,"ratio":0.4433,"hh_meters_2013":307,"hh_meters_2024":882},{"rank":15,"name":"Burnley","code":"E07000117","mean_gwh_per_meter_2013":0.7756,"mean_gwh_per_meter_2024":0.3437,"ratio":0.4431,"hh_meters_2013":176,"hh_meters_2024":447},{"rank":16,"name":"Bolsover","code":"E07000033","mean_gwh_per_meter_2013":1.1524,"mean_gwh_per_meter_2024":0.5105,"ratio":0.443,"hh_meters_2013":150,"hh_meters_2024":369},{"rank":17,"name":"Cambridge","code":"E07000008","mean_gwh_per_meter_2013":0.9911,"mean_gwh_per_meter_2024":0.437,"ratio":0.4409,"hh_meters_2013":424,"hh_meters_2024":1138},{"rank":18,"name":"Nottingham","code":"E06000018","mean_gwh_per_meter_2013":0.6765,"mean_gwh_per_meter_2024":0.2971,"ratio":0.4392,"hh_meters_2013":799,"hh_meters_2024":1778},{"rank":19,"name":"Wandsworth","code":"E09000032","mean_gwh_per_meter_2013":0.5134,"mean_gwh_per_meter_2024":0.2255,"ratio":0.4392,"hh_meters_2013":477,"hh_meters_2024":1441},{"rank":20,"name":"Welwyn Hatfield","code":"E07000241","mean_gwh_per_meter_2013":1.3909,"mean_gwh_per_meter_2024":0.5932,"ratio":0.4265,"hh_meters_2013":264,"hh_meters_2024":680}],"bottom_5":[{"rank":321,"name":"Cheshire West and Chester","ratio":0.1763},{"rank":322,"name":"Pembrokeshire / Sir Benfro","ratio":0.1741},{"rank":323,"name":"Redcar and Cleveland","ratio":0.1676},{"rank":324,"name":"King's Lynn and West Norfolk","ratio":0.154},{"rank":325,"name":"Wokingham","ratio":0.1511}]},"matching_basis_sensitivity":{"note":"The number of authorities in the base depends on how two authorities in different years are judged to be the same authority. All three rules give the same answer to the question asked.","bases":{"reconciled":{"matching_rule":"Reconciled identity: the published name with the Welsh bilingual second form removed, which is identical in result to matching on the ONS code with the two 2016 recodes applied (Barnsley E08000016 to E08000038, Sheffield E08000019 to E08000039). Both give the same set and the same figures.","n":325,"median_ratio":0.2914,"n_at_or_above_parity":1,"at_or_above_parity":["Slough"]},"published_name":{"matching_rule":"The published name exactly as DESNZ writes it in each year's sheet, with no normalisation.","n":303,"median_ratio":0.2901,"n_at_or_above_parity":1,"at_or_above_parity":["Slough"]},"published_code":{"matching_rule":"The published ONS code exactly as given, with no recoding.","n":323,"median_ratio":0.2906,"n_at_or_above_parity":1,"at_or_above_parity":["Slough"]}}},"clean_window":{"note":"The same test over 2019 to 2023, a window that sits after P272 and P322 completed their mandated migration in April 2017 and before the 2024 break, so it needs no argument about what either did. It is not a window with no meters moving at all: half-hourly meters in Great Britain rose 8.5 per cent across it, because P322 continues to move meters as businesses change supplier or contract. It is the quietest window available in this data, not a silent one.","from_year":2019,"to_year":2023,"n":349,"median_ratio":0.8265,"n_at_or_above_parity":6,"at_or_above_parity":[{"name":"Slough","code":"E06000039","ratio":1.4135},{"name":"Three Rivers","code":"E07000102","ratio":1.2931},{"name":"Dacorum","code":"E07000096","ratio":1.1591},{"name":"Hillingdon","code":"E09000017","ratio":1.1217},{"name":"Harlow","code":"E07000073","ratio":1.0395},{"name":"Newport / Casnewydd","code":"W06000022","ratio":1.0089}],"slough_rank":1,"slough_ratio":1.4135},"slough_series":[{"year":2010,"hh_meters":347,"hh_twh":0.5828,"mean_gwh_per_hh_meter":1.6797,"all_non_domestic_gwh":null,"all_meter_gwh":null},{"year":2011,"hh_meters":356,"hh_twh":0.6311,"mean_gwh_per_hh_meter":1.7726,"all_non_domestic_gwh":null,"all_meter_gwh":null},{"year":2012,"hh_meters":365,"hh_twh":0.6884,"mean_gwh_per_hh_meter":1.8859,"all_non_domestic_gwh":812.3,"all_meter_gwh":1013.2},{"year":2013,"hh_meters":383,"hh_twh":0.723,"mean_gwh_per_hh_meter":1.8878,"all_non_domestic_gwh":838.8,"all_meter_gwh":1037.6},{"year":2014,"hh_meters":460,"hh_twh":0.753,"mean_gwh_per_hh_meter":1.637,"all_non_domestic_gwh":870.3,"all_meter_gwh":1071.2},{"year":2015,"hh_meters":401,"hh_twh":0.778,"mean_gwh_per_hh_meter":1.94,"all_non_domestic_gwh":887.9,"all_meter_gwh":1088.6},{"year":2016,"hh_meters":643,"hh_twh":0.8403,"mean_gwh_per_hh_meter":1.3069,"all_non_domestic_gwh":920.3,"all_meter_gwh":1120.3},{"year":2017,"hh_meters":793,"hh_twh":0.9231,"mean_gwh_per_hh_meter":1.164,"all_non_domestic_gwh":988,"all_meter_gwh":1185.7},{"year":2018,"hh_meters":817,"hh_twh":1.0032,"mean_gwh_per_hh_meter":1.2279,"all_non_domestic_gwh":1063.9,"all_meter_gwh":1259.8},{"year":2019,"hh_meters":822,"hh_twh":1.0841,"mean_gwh_per_hh_meter":1.3189,"all_non_domestic_gwh":1142.3,"all_meter_gwh":1338.6},{"year":2020,"hh_meters":822,"hh_twh":1.1394,"mean_gwh_per_hh_meter":1.3862,"all_non_domestic_gwh":1189.9,"all_meter_gwh":1395.6},{"year":2021,"hh_meters":830,"hh_twh":1.2665,"mean_gwh_per_hh_meter":1.5259,"all_non_domestic_gwh":1324.1,"all_meter_gwh":1521.4},{"year":2022,"hh_meters":856,"hh_twh":1.4077,"mean_gwh_per_hh_meter":1.6445,"all_non_domestic_gwh":1462.6,"all_meter_gwh":1649.4},{"year":2023,"hh_meters":841,"hh_twh":1.5679,"mean_gwh_per_hh_meter":1.8643,"all_non_domestic_gwh":1622.3,"all_meter_gwh":1814.1},{"year":2024,"hh_meters":918,"hh_twh":1.7343,"mean_gwh_per_hh_meter":1.8892,"all_non_domestic_gwh":1786.3,"all_meter_gwh":1984.9}]}},{"id":"concentration","order":4,"heading":"Where the growth is, and whether it is real","body":"Over 2019 to 2023, chosen because it sits after P272 finished and before the 2024 break, the picture is a broad decline with a handful of places going the other way, and almost all of the growth sits in ten of them: 326 of 350 local authorities used less, 24 used more, and the ten largest risers account for 94.6 per cent of the 1,093.9 GWh of increases. Because the half-hourly series can be moved by reclassification, every riser is shown here on the all-non-domestic series as well, which a reclassified meter stays inside.","findings":{"half_hourly":{"series":"half-hourly (large-site) electricity","n_local_authorities":350,"n_up":24,"n_down":326,"n_unchanged":0,"total_growth_gwh":1093.9,"total_decline_gwh":-13917.8,"net_change_gwh":-12823.9,"top_k":10,"top_k_growth_gwh":1034.8,"top_k_share_of_total_growth_pct":94.6,"denominator_for_that_share":"the sum of the increases of the 24 local authorities that used more, 1,093.9 GWh; falls are not netted off","top":[{"code":"E06000039","change_gwh":483.7},{"code":"E09000017","change_gwh":196.1},{"code":"E07000096","change_gwh":91.1},{"code":"W06000022","change_gwh":65.3},{"code":"E06000054","change_gwh":57.3},{"code":"E07000102","change_gwh":56},{"code":"E09000009","change_gwh":32.7},{"code":"E07000073","change_gwh":19.9},{"code":"E07000089","change_gwh":17.9},{"code":"E07000218","change_gwh":14.8}]},"all_non_domestic":{"series":"all non-domestic electricity (migration-immune)","n_local_authorities":350,"n_up":13,"n_down":337,"n_unchanged":0,"total_growth_gwh":941.7,"total_decline_gwh":-17807.7,"net_change_gwh":-16866.1,"top_k":10,"top_k_growth_gwh":933.5,"top_k_share_of_total_growth_pct":99.13,"denominator_for_that_share":"the sum of the increases of the 13 local authorities that used more, 941.7 GWh; falls are not netted off","top":[{"code":"E06000039","change_gwh":480},{"code":"E09000017","change_gwh":183.3},{"code":"E07000096","change_gwh":85},{"code":"W06000022","change_gwh":60.7},{"code":"E07000102","change_gwh":50.6},{"code":"E06000054","change_gwh":21.5},{"code":"E09000009","change_gwh":16},{"code":"E07000073","change_gwh":15.1},{"code":"E07000089","change_gwh":13.8},{"code":"E07000218","change_gwh":7.5}]},"top_risers":[{"rank_on_half_hourly":1,"rank_on_all_non_domestic":1,"code":"E06000039","name":"Slough","region":"South East","hh_change_gwh":483.7,"hh_share_of_hh_growth_pct":44.22,"all_non_domestic_change_gwh":480,"all_non_domestic_share_of_that_growth_pct":50.97,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.01},{"rank_on_half_hourly":2,"rank_on_all_non_domestic":2,"code":"E09000017","name":"Hillingdon","region":"Outer London","hh_change_gwh":196.1,"hh_share_of_hh_growth_pct":17.93,"all_non_domestic_change_gwh":183.3,"all_non_domestic_share_of_that_growth_pct":19.46,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":3,"rank_on_all_non_domestic":3,"code":"E07000096","name":"Dacorum","region":"East","hh_change_gwh":91.1,"hh_share_of_hh_growth_pct":8.32,"all_non_domestic_change_gwh":85,"all_non_domestic_share_of_that_growth_pct":9.02,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":4,"rank_on_all_non_domestic":4,"code":"W06000022","name":"Newport / Casnewydd","region":"Wales","hh_change_gwh":65.3,"hh_share_of_hh_growth_pct":5.97,"all_non_domestic_change_gwh":60.7,"all_non_domestic_share_of_that_growth_pct":6.45,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":5,"rank_on_all_non_domestic":6,"code":"E06000054","name":"Wiltshire","region":"South West","hh_change_gwh":57.3,"hh_share_of_hh_growth_pct":5.24,"all_non_domestic_change_gwh":21.5,"all_non_domestic_share_of_that_growth_pct":2.28,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":2.66},{"rank_on_half_hourly":6,"rank_on_all_non_domestic":5,"code":"E07000102","name":"Three Rivers","region":"East","hh_change_gwh":56,"hh_share_of_hh_growth_pct":5.12,"all_non_domestic_change_gwh":50.6,"all_non_domestic_share_of_that_growth_pct":5.37,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.11},{"rank_on_half_hourly":7,"rank_on_all_non_domestic":7,"code":"E09000009","name":"Ealing","region":"Outer London","hh_change_gwh":32.7,"hh_share_of_hh_growth_pct":2.99,"all_non_domestic_change_gwh":16,"all_non_domestic_share_of_that_growth_pct":1.7,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":2.04},{"rank_on_half_hourly":8,"rank_on_all_non_domestic":8,"code":"E07000073","name":"Harlow","region":"East","hh_change_gwh":19.9,"hh_share_of_hh_growth_pct":1.82,"all_non_domestic_change_gwh":15.1,"all_non_domestic_share_of_that_growth_pct":1.6,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.32},{"rank_on_half_hourly":9,"rank_on_all_non_domestic":9,"code":"E07000089","name":"Hart","region":"South East","hh_change_gwh":17.9,"hh_share_of_hh_growth_pct":1.64,"all_non_domestic_change_gwh":13.8,"all_non_domestic_share_of_that_growth_pct":1.47,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.3},{"rank_on_half_hourly":10,"rank_on_all_non_domestic":10,"code":"E07000218","name":"North Warwickshire","region":"West Midlands","hh_change_gwh":14.8,"hh_share_of_hh_growth_pct":1.36,"all_non_domestic_change_gwh":7.5,"all_non_domestic_share_of_that_growth_pct":0.79,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.98}],"agreement":{"same_ten_authorities":true,"same_order":false,"all_ten_up_on_both_series":true,"reading":"The two rankings pick out the same ten local authorities — ten of the 13 that rose at all on the migration-immune series, which is most of that small population by construction. That is still the check that matters: if the half-hourly risers were an artefact of meters being reclassified into the half-hourly category, they would not also be rising on a series that reclassification cannot move."},"largest_divergence":{"name":"Wiltshire","hh_change_gwh":57.3,"all_non_domestic_change_gwh":21.5,"ratio":2.66,"reading":"Wiltshire gained 57.3 GWh of half-hourly load but only 21.5 GWh on the migration-immune series, a factor of 2.7. That gap is a warning sign, and it is why Wiltshire's rise is not treated here as a like-for-like large-site increase. Slough's two figures, 483.7 and 480.0 GWh, and Hillingdon's, 196.1 and 183.3, track each other closely."},"national_context":{"hh_twh_2019":134.204,"hh_twh_2023":121.38,"all_non_domestic_gwh_2019":166587.3,"all_non_domestic_gwh_2023":149721.2,"note":"The two series are not comparable in level and must not be added: half-hourly covers January to December and non-half-hourly February to January, and the all-non-domestic figure contains both."}}},{"id":"data-centre-denominator","order":5,"heading":"The denominator that changes the answer","body":"DESNZ expresses data-centre consumption as a share of all electricity taken from the grid in an area, homes included. That is stated on its own cover sheet. For a question about industrial load it is the wrong denominator: 39.1 per cent of the Great Britain total is domestic. How much difference that makes depends on the area: on the domestic share, which is not uniform — 21.5 per cent in Hillingdon, 18.4 per cent in Tower Hamlets and only 10.0 per cent in Slough — and on how large the published share already is. Recomputed against large-site electricity, the four shares that can be recomputed here, Great Britain and the three published local authorities, rise by between 1.88 and 10.22 percentage points. That recomputation is an approximation: an all-meter numerator over a half-hourly denominator, covering slightly different twelve-month periods. The national figure roughly doubles; Slough's moves by about a seventh, because where data centres already take most of the electricity the two denominators must converge.","findings":{"overlay_2024":[{"area":"Great Britain","is_local_authority":false,"code":null,"year":2024,"data_centre_sites":239,"data_centre_twh":4.4595,"desnz_share_of_all_electricity_pct":1.79,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":39.1,"all_meter_twh_implied":249.2477,"large_site_twh":121.522,"share_of_large_site_electricity_pct":3.67,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 121.5220 TWh","percentage_point_difference":1.88,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Hillingdon","is_local_authority":true,"code":"E09000017","year":2024,"data_centre_sites":10,"data_centre_twh":0.5363,"desnz_share_of_all_electricity_pct":28.13,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":21.5,"all_meter_twh_implied":1.9065,"large_site_twh":1.3983,"share_of_large_site_electricity_pct":38.35,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.3983 TWh","percentage_point_difference":10.22,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Slough","is_local_authority":true,"code":"E06000039","year":2024,"data_centre_sites":30,"data_centre_twh":1.2934,"desnz_share_of_all_electricity_pct":65.16,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":10,"all_meter_twh_implied":1.9849,"large_site_twh":1.7343,"share_of_large_site_electricity_pct":74.58,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7343 TWh","percentage_point_difference":9.42,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Tower Hamlets","is_local_authority":true,"code":"E09000030","year":2024,"data_centre_sites":29,"data_centre_twh":0.4299,"desnz_share_of_all_electricity_pct":18.25,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":18.4,"all_meter_twh_implied":2.3562,"large_site_twh":1.7339,"share_of_large_site_electricity_pct":24.79,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7339 TWh","percentage_point_difference":6.55,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."}],"great_britain_series":[{"year":2020,"data_centre_sites":221,"data_centre_twh":3.1589,"desnz_share_of_all_electricity_pct":1.229,"large_site_twh":118.968,"share_of_large_site_electricity_pct":2.655},{"year":2021,"data_centre_sites":224,"data_centre_twh":3.4448,"desnz_share_of_all_electricity_pct":1.332,"large_site_twh":122.904,"share_of_large_site_electricity_pct":2.803},{"year":2022,"data_centre_sites":230,"data_centre_twh":3.8433,"desnz_share_of_all_electricity_pct":1.539,"large_site_twh":124.246,"share_of_large_site_electricity_pct":3.093},{"year":2023,"data_centre_sites":238,"data_centre_twh":4.1268,"desnz_share_of_all_electricity_pct":1.658,"large_site_twh":121.38,"share_of_large_site_electricity_pct":3.4},{"year":2024,"data_centre_sites":239,"data_centre_twh":4.4595,"desnz_share_of_all_electricity_pct":1.789,"large_site_twh":121.522,"share_of_large_site_electricity_pct":3.67}],"coverage":{"n_areas_published":18,"n_areas_that_are_local_authorities":3,"local_authorities":["Hillingdon","Slough","Tower Hamlets"],"note":"DESNZ publishes eighteen areas and they mix levels: Great Britain, combined regions, regions, residuals such as 'the rest of Outer London', two county-level areas (Hampshire and Greater Manchester) and three local authorities. They must not be summed. Only the three local authorities can be given a large-site denominator from the half-hourly panel, so the overlay can be attached to three of the 325 authorities in the intensity base and no more. Hampshire and Greater Manchester have no single row in the local authority panel, so neither is given a large-site denominator here.","small_n_warning":"Three cases. No percentage is computed across them, and none should be. Each figure below is a ratio for one place."},"label":"Approximation: an all-meter numerator over a half-hourly denominator, covering slightly different twelve-month periods.","series_break_note":"The 2020 to 2024 series below is not a like-for-like trend at its last point. Its denominator is large-site electricity, and the half-hourly meter base jumped 23.41 per cent in 2024 while half-hourly electricity barely moved (121.380 to 121.522 TWh). The 2024 row therefore sits on a different meter basis from 2020 to 2023, and the rise from 2.655 to 3.670 per cent should be read with that in mind rather than as four clean years of growth.","why_it_is_an_approximation":"DESNZ's data-centre numerator is built from all meters matched to a data centre, half-hourly or not, and covers a different twelve months from the half-hourly denominator. On that mismatch alone the ratio leans high, and it is labelled as an approximation everywhere it appears. That is only one of the two biases: the scope exclusion pushes the other way, neither has been quantified, so the net direction of error is not determinable from published data.","understatement":"Two biases run in opposite directions and neither has been quantified, so the net direction of error is not determinable from published data. Scope pushes the true share up: DESNZ counts only colocation, managed hosting and hyperscale data centres serving external organisations, so enterprise data centres are out of scope, as are some smaller in-scope sites and 17 of the 259 identified sites to which no meter could be matched. The construction of the ratio pushes the published figure up: an all-meter numerator sits over a half-hourly denominator, which inflates the share by whatever part of the data-centre load is not on a half-hourly meter. Both are stated; neither is netted off, because nobody has published the size of either."}},{"id":"aggregation-warning","order":6,"heading":"The warning on the front of the file, what it governs, and the one sum we make anyway","body":"The MSOA workbook's cover sheet says, in terms: 'These statistics should not be aggregated to local authority, regional or country level'. It is a fair warning and it is worth answering rather than ignoring. Two sentences on the same cover sheet answer it. 'While these statistics are presented at MSOA level for non-half hourly meters, the data on half hourly meters (which is far more disclosive) is only broken down by local authority.' The half-hourly rows carry the MSOA code 'All MSOAs' and a local authority name, because DESNZ publishes them at local authority level itself. This study reads only those rows. It never builds a local authority total out of MSOA rows, which is what the warning is about. The subnational workbook, the local authority product the warning redirects users to, carries no such warning, and it is the series every riser is ranked on here. The warning does name country level as well, and one country-level sum is made here, so it is set out below with what was and was not checked about it.","findings":{"what_we_read":"Half-hourly rows only, as published at local authority level.","what_we_never_do":"Sum MSOA rows to make a local authority, a region or a country.","one_national_sum_we_do_make":"Great Britain's half-hourly total for a year, 121.522 TWh in 2024, which is the sum of the already-local-authority-level half-hourly rows and is the denominator of the data-centre share below. DESNZ publishes no half-hourly national total to check it against: neither workbook splits a national row into half-hourly and non-half-hourly, so no external reconciliation of this sum is possible and none is claimed. What has been checked is that the rows being added are complete and do not overlap. The 350 local authorities in the 2024 half-hourly sheet are exactly the 350 DESNZ publishes in its own local authority workbook for that year, name for name; the published mean per meter equals total over meters on every row; and the Unallocated row is held out and reported on its own. The defence of the sum is the cover sheet's own statement that these rows are published at local authority level, not a reconciliation.","unallocated":{"note":"MSOAs with fewer than five meters are moved to an 'Unallocated' row for disclosure control, so no set of area rows is a complete national total. Unallocated is reported separately here and never folded into a local authority or silently dropped.","by_year":[{"year":2010,"unallocated_hh_meters":4890,"unallocated_hh_twh":5.8181},{"year":2011,"unallocated_hh_meters":4061,"unallocated_hh_twh":5.5641},{"year":2012,"unallocated_hh_meters":4486,"unallocated_hh_twh":5.8456},{"year":2013,"unallocated_hh_meters":4437,"unallocated_hh_twh":5.8954},{"year":2014,"unallocated_hh_meters":4973,"unallocated_hh_twh":5.7937},{"year":2015,"unallocated_hh_meters":1700,"unallocated_hh_twh":2.713},{"year":2016,"unallocated_hh_meters":2316,"unallocated_hh_twh":2.8364},{"year":2017,"unallocated_hh_meters":2695,"unallocated_hh_twh":2.8858},{"year":2018,"unallocated_hh_meters":2705,"unallocated_hh_twh":2.8454},{"year":2019,"unallocated_hh_meters":2692,"unallocated_hh_twh":2.7073},{"year":2020,"unallocated_hh_meters":2697,"unallocated_hh_twh":2.4237},{"year":2021,"unallocated_hh_meters":2786,"unallocated_hh_twh":2.6852},{"year":2022,"unallocated_hh_meters":2829,"unallocated_hh_twh":2.6763},{"year":2023,"unallocated_hh_meters":2835,"unallocated_hh_twh":2.6307},{"year":2024,"unallocated_hh_meters":4132,"unallocated_hh_twh":2.6826}]}}}],"caveats":["2024 figure. A large reclassification break appears in the 2024 half-hourly data: half-hourly meters rose 23.6 per cent in one year, or 23.4 per cent with the Unallocated row left out, while total non-domestic meters rose 1.3 per cent, and 344 of the 349 local authorities with at least 100 half-hourly meters in 2023 gained more than 5 per cent. No explanation for it appears in the documents read here. It is not Market-wide Half Hourly Settlement: Ofgem's CR055 decision puts MHHS meter migration between late October 2025 and May 2027, after this data year. Any 2024 figure on this page sits on a meter base that earlier years do not share.","Settlement migration, not demand. BSC modification P272, with P322 alongside it, moved profile classes 5 to 8 into half-hourly settlement between 5 November 2015 and 1 April 2017. Ofgem states the condition: 'These changes only apply to non-domestic businesses that are in profile classes 5-8 and have an advanced meter installed.' The migration was therefore partial, and P322 keeps moving meters after 2017 as businesses change supplier or contract. Half-hourly meters in Great Britain went from 127,478 in 2015 to 265,975 in 2017 while the average per meter fell from 0.9916 to 0.5093 GWh. That fall is reclassification, not a change in electricity use.","Measuring per meter reduces that distortion but does not remove it: the meters that moved in are smaller than the ones already there, so the per-meter mean is pushed down wherever migration happened, which is almost everywhere. The 2019 to 2023 test is reported alongside for exactly this reason: it sits between the two documented settlement breaks. Even that window is not still — half-hourly meters rose 8.5 per cent across it — so it is the quietest window in the data rather than a clean one.","A 'large site' here is a meter, not a building and not a business. DESNZ splits domestic from non-domestic by settlement profile class, with profile 1 and 2 meters reallocated to non-domestic above 100,000 kWh a year, or above 50,000 kWh with supporting address information. A site with several meters counts several times; a single meter serving several businesses counts once.","Half-hourly data covers January to December. Non-half-hourly data covers February to January; the 2024 non-half-hourly year is February 2024 to January 2025. The two are never added here, and the all-non-domestic series used for the migration-immune cross-check contains both, so it mixes the two periods as well.","The data-centre share of large-site electricity divides an all-meter numerator by a half-hourly denominator. It is an approximation and is labelled as one wherever it appears.","DESNZ's data-centre statistics cover 239 operational sites in Great Britain in 2024 and count only colocation, managed hosting and hyperscale sites serving external organisations. Enterprise data centres are excluded, so the scope exclusion pushes the true share above what the overlay shows. A second bias runs the other way: an all-meter numerator sits over a half-hourly denominator, which inflates the figure the overlay reports. Neither has been quantified, so the net direction of error is not determinable from published data.","DESNZ classifies the data-centre statistics as Official Statistics in Development, which in its own words carry a higher degree of uncertainty than Official Statistics.","Geography break at 2015. The 2010 to 2014 years use 2011 Census geographies and carry 370 to 371 local authorities; 2015 onwards uses 2021 (England and Wales) and 2022 (Scotland) geographies and carries exactly 350. No single local authority set spans 2010 to 2024, which is why no figure here is anchored on 2010.","Revisions. DESNZ revises 2015 onwards at each annual publication, as postcode lookups are updated, meter addresses corrected and anomalous year-on-year changes investigated. Years to 2014 are not revised on the same basis. These figures are the 18 December 2025 edition of the half-hourly and subnational workbooks and the 30 June 2026 edition of the data-centre tables. A later edition will not reproduce them exactly. One headline figure is thin enough for that to matter: Slough clears parity by 0.08 per cent, or 0.0014 GWh per meter, so a revision of a tenth of one per cent to its 2024 mean would move the parity count from one to none. Nothing else in the study turns on a margin that fine.","The number of local authorities in the intensity base depends on how an authority in one year is matched to an authority in another. Matching on the published name gives 303, because DESNZ writes twenty-two Welsh authorities bilingually in 2024 and monolingually in 2013. Matching on the published code gives 323, because Barnsley and Sheffield were recoded in 2016. The reconciled basis used here gives 325. The finding is the same on all three.","MSOAs with fewer than five meters are moved to an 'Unallocated' row for disclosure control. In 2024 that row holds 4,132 half-hourly meters and 2.6826 TWh. It is reported separately and is excluded from every local authority figure and from the national large-site denominator.","DESNZ's subnational data excludes Central Volume Allocation users and electricity generated and consumed on site. Some of the largest sites in the country may therefore sit outside the large-site denominator entirely.","Only three of the eighteen areas in the data-centre tables are local authorities. The data-centre overlay can be attached to three authorities and no more. There is no published per-authority data-centre figure for the rest.","Market-wide Half Hourly Settlement will migrate 33 million MPANs between late October 2025 and May 2027. It will contaminate the 2025, 2026 and 2027 data years far more severely than P272 did. Any comparison drawn through those years will need the same treatment this study gives P272, or worse.","The PDF text of the DESNZ special article runs superscript footnote markers into the preceding number, so '2423' is 242 with footnote 3 and '2594' is 259 with footnote 4. 242 matched plus 17 unmatched is 259 identified, and the published tables give 239 operational in 2024. Anyone re-extracting that PDF should not read those as 2,423 or 2,594.","We have not read the current edition of DESNZ's subnational energy statistics methodology note. We could not locate a December 2025 edition at a stable address, and nothing here depends on it: the defence of what is aggregated rests on the cover sheet of the workbook itself.","Nothing here identifies a site, an operator or a person. The unit throughout is a local authority."],"method":{"what_was_measured":"Three things. First, electricity per half-hourly (large-site) meter by local authority, 2013 against 2024, as a ratio, over authorities with more than 100 half-hourly meters in 2013. Second, the direction and concentration of change in large-site electricity by local authority over 2019 to 2023, computed twice: once on the half-hourly series and once on the all-non-domestic series that reclassification cannot move. Third, data-centre electricity as a share of large-site electricity, where DESNZ publishes it as a share of all electricity including homes.","when":"Source files downloaded 2026-09-20T06:48Z. The half-hourly and subnational workbooks are the 18 December 2025 editions, covering data years to 2024; the data-centre tables are the 30 June 2026 edition, covering 2020 to 2024. Analysis computed 2026-09-20.","population":{"definition":"Every local authority in Great Britain that appears in the half-hourly rows of the DESNZ MSOA non-domestic electricity workbook in any year from 2010 to 2024, identified on the reconciled basis. This is a population, not a sample.","n":378,"n_in_2024":350,"n_in_2013":371,"panel_rows":5369,"la_year_observations":5354,"unallocated_rows":15,"matched_panels":{"intensity_base_2013_to_2024":325,"present_in_every_year_2015_to_2024":350,"present_in_every_year_2010_to_2024":342,"clean_window_base_2019_to_2023":349,"concentration_base_2019_to_2023":350},"rows_per_year":{"2010":370,"2011":371,"2012":371,"2013":371,"2014":371,"2015":350,"2016":350,"2017":350,"2018":350,"2019":350,"2020":350,"2021":350,"2022":350,"2023":350,"2024":350}},"how":["All four DESNZ files were downloaded once, with byte size and md5 recorded, and nothing was fetched twice. Requests were sequential, half a second apart, with an identifying user agent. www.gov.uk robots.txt permits the paths used; the assets host serves no robots.txt.","openpyxl is not available in this environment, so the workbooks were read by unzipping the xlsx and parsing the sheet XML directly. Sheets were selected by name, never by position, because the sheet order is not chronological.","Columns were matched by header text, never by position, because the subnational workbook changes its headers in 2012 from 'Domestic' and 'Non-Domestic' to 'All Domestic' and 'All Non-Domestic'.","Only the half-hourly rows of the MSOA workbook were used. Those rows are published by DESNZ at local authority level and carry the MSOA code 'All MSOAs'. No MSOA row was ever aggregated.","The 'Unallocated' rows were kept, flagged and excluded from every total, never silently dropped.","Local authorities were matched across years on a reconciled identity: the published name with the Welsh bilingual second form removed, which gives the same set as matching on the ONS code with the two 2016 recodes applied. All three possible rules were computed and are reported.","The intensity test is the ratio of DESNZ's own published mean kWh per half-hourly meter in 2024 to 2013. The published mean was checked against total kWh divided by meter count on all 5354 local authority rows and agreed on every one, so nothing was recomputed.","The concentration window is 2019 to 2023, chosen because P272 completed on 1 April 2017 and the unexplained break falls in 2024, so the window contains neither.","The migration-immune cross-check uses all non-domestic electricity from the subnational workbook. A meter moved between half-hourly and non-half-hourly settlement stays inside that total, so the total cannot be moved by reclassification alone.","The data-centre overlay divides DESNZ's published data-centre TWh by the half-hourly TWh for the same area and year. It is labelled an approximation because the numerator is an all-meter figure and the two figures cover slightly different twelve-month periods.","Two reconciliations were run as blocking checks before any analysis: DESNZ's published data-centre TWh divided by its published share returns the subnational all-meter total exactly, for Great Britain and for Slough. Both agreed to eight decimal places.","No network access takes place at analysis time. The script reads only local files and is deterministic."],"why_2013":"P272, with P322 alongside it, moved meters into half-hourly settlement between 5 November 2015 and 1 April 2017, so 2013 and 2014 are both before settlement migration. 2013 is used rather than 2014 because the printed national series moves sharply between them: half-hourly meters rise from 121,327 in 2013 to 145,104 in 2014 and fall back to 127,478 in 2015, across the change of geography basis, so 2014 is the noisier of the two base years. 2013 is the last quiet year in which the half-hourly category meant what it had meant for the previous decade.","why_more_than_100_meters":"Below about a hundred half-hourly meters a single large site moves the mean, and a single reclassification moves it further. The threshold is a judgement, stated here so it can be varied: it excludes 21 of the 371 authorities present in 2013.","denominators_in_use":[{"name":"all electricity","definition":"all electricity taken from the grid in an area, domestic and non-domestic","used_by":"DESNZ, for the data-centre shares it publishes","gb_2024_twh":249.248},{"name":"large-site (half-hourly) electricity","definition":"electricity on half-hourly settled meters, which is DESNZ's own definition of the larger non-domestic sites","used_by":"this study","gb_2024_twh":121.522,"note":"excludes the Unallocated row; 2.6826 TWh sits there in 2024"},{"name":"all non-domestic electricity","definition":"half-hourly plus non-half-hourly non-domestic meters, as published in the subnational workbook","used_by":"this study, for the migration-immune cross-check only","gb_2024_twh":151.744}],"corrections_to_the_brief":[{"what_the_brief_said":"That Market-wide Half Hourly Settlement moved meters into the half-hourly category in 2024, and that every figure ending in 2024 must carry an MHHS caveat.","what_the_evidence_shows":"Ofgem's CR055 decision of 29 November 2024 puts MHHS meter migration between late October 2025 and May 2027. No MHHS migration happened in the 2024 electricity year.","what_was_done":"The 2024 break is real, is measured and is caveated, but it is described as unexplained in the DESNZ documents read here rather than attributed to MHHS. MHHS carries a separate, forward-looking caveat about the 2025 to 2027 data years."},{"what_the_brief_said":"That the intensity base is n=303.","what_the_evidence_shows":"303 is what literal name matching gives, because it drops twenty-two Welsh authorities over a bilingual spelling change between 2013 and 2024.","what_was_done":"The reconciled basis is used, n=325, and all three bases are published. The finding does not change: exactly one authority at or above parity and a median of 0.29 on every basis."},{"what_the_brief_said":"That the intensity base is drawn from 303 of 350 authorities 'with a meaningful large-site base'.","what_the_evidence_shows":"350 of the 371 authorities present in 2013 had more than 100 half-hourly meters; the losses between 2013 and 2024 are local government reorganisation, not a lack of large sites.","what_was_done":"Both numbers are reported, and the reason authorities drop out is stated."},{"what_the_brief_said":"That the matched panel for 2010 to 2024 is n=318.","what_the_evidence_shows":"On the same reconciled identity basis used everywhere else, 342 local authorities appear in all fifteen years. The other two bases give 340 (published code) and 320 (published name). None of the three gives 318, and the brief does not say how it was reached.","what_was_done":"The reconciled figure, n=342, is published, for the same reason the intensity base is 325 rather than 303. Nothing in the study rests on the 2010 to 2024 panel: the geography break at 2015 is why no headline is anchored on 2010."}],"personal_data":"None. The unit of analysis is a local authority. The source documents name authors, responsible statisticians and press contacts and carry departmental mailboxes; those were stripped from every derived text before anything was written, by scripts/research/uk-large-site-electricity-data-centres-2026/evidence_redact.py, which holds the names it strips as salted hashes so that no name is retained in the repository either. No individual is named in the dataset, the README, the page or any working file.","outbound_contact":"None. No email, request or notice of any kind was sent to anyone. Everything here comes from already-published statistics.","reproducibility":"scripts/research/uk-large-site-electricity-data-centres-2026/analyse.py reads the three tidy panels in data/research/uk-large-site-electricity-data-centres-2026/ and writes all three published files. It performs no network access and is deterministic: running it twice on the same inputs produces byte-identical output. The panels themselves are rebuilt from the raw workbooks by build_panels.py in the same directory, and the raw workbooks carry recorded md5s."},"sources":[{"id":"desnz_msoa_nondom","name":"Non-domestic electricity consumption by Middle Layer Super Output Area (MSOA), Great Britain, 2010 to 2024","publisher":"Department for Energy Security and Net Zero","landing_url":"https://www.gov.uk/government/statistics/lower-and-middle-super-output-areas-electricity-consumption","file_url":"https://assets.publishing.service.gov.uk/media/69427b3736f089d38be1f1ce/MSOA_non-domestic_elec_2010-2024.xlsx","collection_url":"https://www.gov.uk/government/collections/sub-national-electricity-consumption-data","published":"2025-12-18","retrieved":"2026-09-20T06:48Z","bytes":9857810,"md5":"b5d5d28623949b003e46332834c05135","licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"The half-hourly rows only. In this workbook those rows carry the MSOA code 'All MSOAs' and a local authority name, because DESNZ publishes half-hourly data at local authority level and not below it. Meter counts, total kWh and the published mean kWh per meter, 2010 to 2024.","role":"The large-site panel. Both headline measures are computed from it."},{"id":"desnz_subnational_la","name":"Subnational electricity consumption statistics, Great Britain, 2005 to 2024","publisher":"Department for Energy Security and Net Zero","landing_url":"https://www.gov.uk/government/statistics/regional-and-local-authority-electricity-consumption-statistics","file_url":"https://assets.publishing.service.gov.uk/media/69426e905431f4f94d7f0b5e/Subnational_electricity_consumption_statistics_2005-2024.xlsx","collection_url":"https://www.gov.uk/government/collections/sub-national-electricity-consumption-data","published":"2025-12-18","retrieved":"2026-09-20T06:48Z","bytes":2103254,"md5":"4b6ec832be2747350f1a512506d0404a","licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"Domestic, non-domestic and all-meter GWh and meter counts by local authority, region and country. Used as the migration-immune series: a meter moved between half-hourly and non-half-hourly settlement stays inside the all-non-domestic total, so that total cannot be moved by reclassification alone.","role":"The migration-immune cross-check, and the source of the all-meter denominator DESNZ itself uses."},{"id":"desnz_dc_tables","name":"Energy Trends June 2026 special feature: data centre electricity consumption in Great Britain, 2020 to 2024 (data tables)","publisher":"Department for Energy Security and Net Zero","landing_url":"https://www.gov.uk/government/publications/energy-trends-june-2026-special-feature-article-data-centre-electricity-consumption-in-great-britain-2020-to-2024","file_url":"https://assets.publishing.service.gov.uk/media/6a3e9f32eaee00074150f678/Data_centre_electricity_consumption_in_Great_Britain__2020_to_2024.xlsx","collection_url":"https://www.gov.uk/government/collections/energy-trends","published":"2026-06-30","retrieved":"2026-09-20T06:48Z","bytes":60596,"md5":"3c91b3ed10c274d3d939e7de409ad4f0","licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"Tables 1 to 3: operational site counts, TWh and the published share of area electricity, for eighteen areas over 2020 to 2024.","role":"The data-centre overlay. Official Statistics in Development, in DESNZ's own classification.","scope_warning":"Covers colocation, managed hosting and hyperscale data centres serving external organisations. Enterprise data centres, run by an organisation for its own IT, are excluded, so the scope exclusion pushes the true share above what the overlay shows. A second bias runs the other way: the overlay puts an all-meter numerator over a half-hourly denominator, which inflates the figure it reports. Neither has been quantified, so the net direction of error is not determinable from published data."},{"id":"desnz_dc_article","name":"Energy Trends June 2026 special feature article: data centre electricity consumption in Great Britain, 2020 to 2024 (article)","publisher":"Department for Energy Security and Net Zero","landing_url":"https://www.gov.uk/government/publications/energy-trends-june-2026-special-feature-article-data-centre-electricity-consumption-in-great-britain-2020-to-2024","retrieved":"2026-09-20T06:48Z","bytes":214845,"md5":"420aed4ea6b48df0e0beef76ca183bc1","licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"Scope, method and the comparisons DESNZ draws with NESO and ND-NEED.","role":"Scope limits and the published disagreements between estimates."},{"id":"desnz_summary_2024","name":"Subnational electricity and gas consumption summary report 2024","publisher":"Department for Energy Security and Net Zero","landing_url":"https://www.gov.uk/government/statistics/subnational-electricity-and-gas-consumption-summary-report-2024","retrieved":"2026-09-20T06:48Z","bytes":1943868,"md5":"44d800f32901bace37c0b73d79b22bdf","licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"The classification rules: profile class 0 is half-hourly and 1 to 8 are not; profile 5 to 8 are higher-consuming non-domestic meters; profile 1 and 2 meters are reallocated to non-domestic above 100,000 kWh a year, or above 50,000 kWh with supporting address information. Also the statement that the subnational data excludes Central Volume Allocation users and on-site generation.","role":"Definitions, and the department's own warning about per-meter means."},{"id":"ofgem_p272_guidance","name":"Moving to half-hourly energy reads (BSC P272 and P322): a guide for businesses","publisher":"Ofgem","landing_url":"https://www.ofgem.gov.uk/guidance/moving-half-hourly-energy-reads-bsc-p272-and-p322-guide-businesses","retrieved":"2026-09-20T06:48Z","bytes":214562,"licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"The P272 and P322 dates and scope, including the condition Ofgem states: 'These changes only apply to non-domestic businesses that are in profile classes 5-8 and have an advanced meter installed.'","role":"Dates the first settlement-migration break."},{"id":"ofgem_cr055","name":"Decision on Market-wide Half Hourly Settlement Change Request CR055","publisher":"Ofgem","landing_url":"https://www.ofgem.gov.uk/sites/default/files/2024-11/CR055_decision_document.pdf","retrieved":"2026-09-20T06:48Z","bytes":329773,"licence":"Open Government Licence v3.0","licence_url":"https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/","what_was_taken":"The MHHS migration timetable: migration of MPANs begins late October 2025 and completes May 2027, covering 33 million MPANs.","role":"Rules MHHS out as the cause of the 2024 break, and dates the contamination that will affect the 2025 to 2027 data years."},{"id":"commons_library","name":"Data centres: planning policy, sustainability, and resilience (CBP-10315)","publisher":"House of Commons Library","landing_url":"https://commonslibrary.parliament.uk/research-briefings/cbp-10315/","mirror_url":"https://majorprojects.org/wp-content/uploads/2026/04/CBP-10315.pdf","published":"3 November 2025","edition_held":"The 3 November 2025 edition, read from a public mirror at majorprojects.org, not from parliament.uk. The mirrored PDF was not compared against an official copy, because no official copy could be retrieved.","retrieved":"2026-09-20T06:48Z, from a public mirror","licence":"Open Parliament Licence v3.0","licence_url":"https://www.parliament.uk/site-information/copyright-parliament/open-parliament-licence/","what_was_taken":"Comparative context only: the Dublin figure and the national estimates the briefing reports, each with the body the briefing itself credits for it.","role":"Context, and one of the disagreeing national estimates.","limitation":"commonslibrary.parliament.uk and researchbriefings.files.parliament.uk both returned HTTP 403 to our identified fetcher, so the copy held is a public mirror rather than an official one. A later edition dated 27 May 2026 exists and was not retrieved, so no figure from that edition is used."},{"id":"utility_bidder","name":"The cost of UK business energy","publisher":"Utility Bidder","landing_url":"https://www.utilitybidder.co.uk/blog/cost-of-uk-business-energy/","published":"last updated 27 February 2026","retrieved":"not retrieved by our fetcher (HTTP 403)","licence":"Third-party publication. Cited as prior art in the method only. No data taken from it.","what_was_taken":"Nothing quantitative enters this study. It is credited as prior work, and its published method is described so that readers can see how ours differs.","role":"Prior art.","used_as_basis":false,"limitation":"A direct request with our identifying User-Agent returned HTTP 403 and we did not disguise it or retry. The description of their method given here came back through a general-purpose fetch tool rather than our own fetcher, and is therefore not independently verified: treat it as our reading of their page, not as checked fact. No figure of theirs is reproduced and no data from them is used."},{"id":"lbc","name":"Why does the UK have so many data centres, why are they controversial, and where are they?","publisher":"LBC","landing_url":"https://www.lbc.co.uk/article/why-uk-data-centres-where-5Hjdh6R_2/","published":"2026-09-07","retrieved":"not retrieved by our fetcher; quoted from a general-purpose fetch tool","licence":"Third-party publication. Quoted as coverage under fair quotation. No data taken from it.","what_was_taken":"Two figures, quoted only to show how widely the denominators differ in general coverage: 'nearly 500' data centres in the UK, and a statement that data centres used one fifth of the UK's total energy in 2023.","role":"Coverage, and one of the disagreeing national estimates.","used_as_basis":false,"limitation":"Not independently verified. The quotes came back through a general-purpose fetch tool, not our own identified fetcher, and we have not checked what the one-fifth figure is a fifth of, or where LBC took it from. It is reported here as a quoted position with an unstated denominator, not as a figure we have tested."}],"disagreements":[{"about":"How much electricity data centres in Great Britain used in 2023","positions":[{"source":"DESNZ, Energy Trends June 2026 special feature","figure":"4.1 TWh, which the article quotes once as its Great Britain total and once as its England and Wales total; the published table gives 4.1268 TWh for Great Britain","scope":"colocation, managed hosting and hyperscale serving external organisations"},{"source":"National Energy System Operator, as reported by DESNZ","figure":"7.6 TWh for Great Britain in 2023","scope":"built from data-centre capacity with assumptions about utilisation"},{"source":"DESNZ ND-NEED, as reported by DESNZ","figure":"2.6 TWh for England and Wales in 2023","scope":"a different DESNZ data framework"}],"our_position":"We do not pick between them. This study uses the DESNZ special-feature figures because they are the only ones published by area, and the spread between the three estimates is roughly three to one, which is the honest measure of how well this is known. One ambiguity is DESNZ's own and is left standing rather than resolved: the article rounds the same 4.1 TWh to Great Britain when comparing itself with NESO and to England and Wales when comparing itself with ND-NEED. The published table gives 4.1268 TWh for Great Britain in 2023, and that is the figure used here."},{"about":"How many data centres there are","positions":[{"source":"DESNZ data tables","figure":"239 operational in Great Britain in 2024; 259 identified, of which 17 could not be matched to a meter"},{"source":"techUK, November 2024, as reported by the House of Commons Library (3 November 2025 edition)","figure":"450 in the UK"},{"source":"LBC, 7 September 2026","figure":"nearly 500 in the UK","scope":"quoted, not verified; see the sources table"}],"our_position":"The counts are not measuring the same thing. DESNZ counts sites it could match to a meter, in a defined commercial scope, in Great Britain; the others count data centres in the UK on wider definitions that include enterprise sites. Only the DESNZ count is used here, and only alongside DESNZ's own consumption figures. The 450 figure is techUK's, carried by the Commons Library at footnote 19; the LBC figure is quoted from its article and has not been independently checked."},{"about":"Data centres as a share of national electricity","positions":[{"source":"DESNZ","figure":"1.79 per cent of all electricity taken from the grid in Great Britain in 2024","denominator":"all electricity, domestic and non-domestic"},{"source":"A House of Lords answer of 27 January 2025, as reported by the House of Commons Library","figure":"an estimated 2.5 per cent of the UK's electricity","denominator":"not stated in the same terms; a different geography and a wider data-centre definition"},{"source":"LBC, 7 September 2026","figure":"one fifth of the UK's total energy in 2023","denominator":"not stated; quoted, not verified"}],"our_position":"The three figures are not comparable and only one of them is a measurement we can trace. The 2.5 per cent is a parliamentary answer the Commons Library carries at footnote 125, not the Library's own estimate. The LBC figure is quoted as published and has not been independently checked; it says 'energy' rather than electricity and names no denominator, and at face value it sits an order of magnitude above DESNZ's measured share, so it is reported as a position and is not used for anything. Our own figure for 2024, 3.67 per cent, is on a third denominator again, large-site electricity, and is labelled as such everywhere."},{"about":"What a per-meter intensity measure should be measured over","positions":[{"source":"Utility Bidder, February 2026","figure":"mean kWh per non-domestic meter, 2020 against 2024, by local authority","scope":"as their page describes it; we were refused access and have not checked it"},{"source":"This study","figure":"mean kWh per half-hourly (large-site) meter, 2013 against 2024, on the 2013 large-site base, with a 2019 to 2023 clean-window test alongside"}],"our_position":"These are different measures and both are defensible. Ours is narrower on purpose: it is restricted to half-hourly (large-site) meters and to authorities that had a large-site base in 2013, where a per non-domestic meter mean is dominated by small meters. The trade runs against us on one point, and it is stated rather than argued away: their denominator, all non-domestic meters, is the one reclassification cannot move, and ours is the one it can, which is why the migration-immune cross-check and the 2019 to 2023 window exist here. We have not independently verified Utility Bidder's figures and do not present them as checked."},{"about":"Whether the 2024 jump in half-hourly meters has a published cause","positions":[{"source":"DESNZ","figure":"no explanation appears in the 2024 summary report or on the cover sheets of the three workbooks used here","scope":"we did not read the current subnational energy statistics methodology note, which we could not locate at a stable address"},{"source":"The study brief this work was commissioned against","figure":"attributed it to Market-wide Half Hourly Settlement"},{"source":"Ofgem CR055, 29 November 2024","figure":"MHHS meter migration begins late October 2025 and completes May 2027"}],"our_position":"The break is real and measured, and it is not MHHS, which had not begun. Whether DESNZ explains it somewhere we did not look is an open question: the MSOA cover sheet points readers to a subnational energy statistics methodology note for discrepancies of this kind, and we could not obtain a current edition of that note. The break is therefore described here as unexplained in the documents we read, which are named, rather than as unexplained anywhere."}],"prior_art":[{"who":"Department for Energy Security and Net Zero","what":"Energy Trends June 2026 special feature on data centre electricity consumption in Great Britain, 2020 to 2024","published":"30 June 2026","finding":"Data centres accounted for “around two-thirds (65%)” of all electricity consumed from the grid in Slough in 2024, in DESNZ's own words.","how_ours_differs":"Same numerator, different denominator. We recompute it against large-site electricity rather than all electricity including homes."},{"who":"Utility Bidder","what":"A local authority league table with a per-meter intensity measure","published":"last updated 27 February 2026","finding":"Slough highest in the UK on mean consumption per non-domestic meter in 2024, on a 2020 to 2024 comparison. Described here as their page presents it; we reproduce none of their figures.","how_ours_differs":"Per half-hourly meter rather than per non-domestic meter, 2013 rather than 2020 as the base year, restricted to authorities that had a large-site base in 2013, with the settlement-migration artefact measured and a second test over a window between the two settlement breaks.","verification":"Not independently verified. A request with our identifying user agent returned HTTP 403 and we did not disguise it or retry; what we know of their page came back through a general-purpose fetch tool instead. No data from them is used."},{"who":"House of Commons Library","what":"Data centres: planning policy, sustainability, and resilience (CBP-10315)","published":"3 November 2025 edition held; a 27 May 2026 edition exists and was not retrieved","finding":"Carries two figures used here as context, each from a body the briefing itself credits: an estimated 2.5 per cent of the UK's electricity, which the briefing attributes to a House of Lords answer of 27 January 2025; and 48 per cent of electricity consumption in the Dublin area in 2023, which it attributes to the Commission for Regulation of Utilities.","how_ours_differs":"National and international context rather than a local authority measure. The Dublin figure is the nearest published city-region measure we found, but the briefing does not state its denominator, so it cannot be set against Slough's 74.6 per cent of large-site electricity or DESNZ's 65 per cent of all electricity as a like-for-like comparison, and it is not used as one.","verification":"Read from a public mirror of the 3 November 2025 edition; parliament.uk refused our fetcher. Both figures are the briefing's citations of other bodies, not the Library's own estimates."}],"novelty":{"claim":"Two measures that we could not find published anywhere: electricity per half-hourly meter by local authority on a 2013 base with settlement migration handled, and the data-centre share of large-site rather than all electricity.","basis":"DESNZ publishes the inputs and publishes the data-centre share against an all-electricity denominator, stated on its own cover sheet. Utility Bidder publishes a per non-domestic meter measure on a 2020 base. Neither measure here is either of those.","not_claimed":"Not that we are first to notice Slough, first to notice the national decline, or first to build a local authority league table. All three have been published."},"dataset":{"csv":"/research/uk-large-site-electricity-data-centres-2026.csv","readme":"/research/uk-large-site-electricity-data-centres-2026-README.txt","rows":378,"unit":"one local authority","licence":"Open Government Licence v3.0 for the source figures; Creative Commons Attribution 4.0 International (CC BY 4.0) for the derived columns","attribution":"Contains public sector information licensed under the Open Government Licence v3.0.","csv_sha256":"9d1c3f5fc1753eee2ba631d6ffd719f8372fcb4eef7cc45cda4a161bf4596862","readme_sha256":"3102f0c43c67541534c89abdf0923de2f05feff45ca3b0417dcbc2d8990d190e"},"headline":"Of the 325 local authorities in Great Britain with more than 100 half-hourly meters in 2013 and still present in 2024, one has an average half-hourly meter drawing as much electricity now as it did then: Slough, 1.8892 GWh against 1.8878 GWh. The median authority is at 29 per cent, and Great Britain's own mean fell to a ratio of 0.301 over the same period, so the median authority roughly tracks the national reclassification. Between 2019 and 2023, 326 of 350 local authorities used less large-site electricity and 24 used more, and the ten largest risers account for 94.6 per cent of the 1,093.9 GWh of increases, with falls not netted off."},"data":{"gb_half_hourly_series":[{"year":2010,"local_authorities":370,"hh_meters":112514,"hh_twh":126.177,"mean_gwh_per_hh_meter":1.1214,"unallocated_hh_meters":4890,"unallocated_hh_twh":5.8181,"geography_basis":"2011 Census geographies"},{"year":2011,"local_authorities":371,"hh_meters":109195,"hh_twh":117.593,"mean_gwh_per_hh_meter":1.0769,"unallocated_hh_meters":4061,"unallocated_hh_twh":5.5641,"geography_basis":"2011 Census geographies"},{"year":2012,"local_authorities":371,"hh_meters":118095,"hh_twh":124.145,"mean_gwh_per_hh_meter":1.0512,"unallocated_hh_meters":4486,"unallocated_hh_twh":5.8456,"geography_basis":"2011 Census geographies"},{"year":2013,"local_authorities":371,"hh_meters":121327,"hh_twh":126.608,"mean_gwh_per_hh_meter":1.0435,"unallocated_hh_meters":4437,"unallocated_hh_twh":5.8954,"geography_basis":"2011 Census geographies"},{"year":2014,"local_authorities":371,"hh_meters":145104,"hh_twh":125.63,"mean_gwh_per_hh_meter":0.8658,"unallocated_hh_meters":4973,"unallocated_hh_twh":5.7937,"geography_basis":"2011 Census geographies"},{"year":2015,"local_authorities":350,"hh_meters":127478,"hh_twh":126.402,"mean_gwh_per_hh_meter":0.9916,"unallocated_hh_meters":1700,"unallocated_hh_twh":2.713,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2016,"local_authorities":350,"hh_meters":211531,"hh_twh":128.331,"mean_gwh_per_hh_meter":0.6067,"unallocated_hh_meters":2316,"unallocated_hh_twh":2.8364,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2017,"local_authorities":350,"hh_meters":265975,"hh_twh":135.471,"mean_gwh_per_hh_meter":0.5093,"unallocated_hh_meters":2695,"unallocated_hh_twh":2.8858,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2018,"local_authorities":350,"hh_meters":280754,"hh_twh":136.747,"mean_gwh_per_hh_meter":0.4871,"unallocated_hh_meters":2705,"unallocated_hh_twh":2.8454,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2019,"local_authorities":350,"hh_meters":288854,"hh_twh":134.204,"mean_gwh_per_hh_meter":0.4646,"unallocated_hh_meters":2692,"unallocated_hh_twh":2.7073,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2020,"local_authorities":350,"hh_meters":289457,"hh_twh":118.968,"mean_gwh_per_hh_meter":0.411,"unallocated_hh_meters":2697,"unallocated_hh_twh":2.4237,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2021,"local_authorities":350,"hh_meters":292431,"hh_twh":122.904,"mean_gwh_per_hh_meter":0.4203,"unallocated_hh_meters":2786,"unallocated_hh_twh":2.6852,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2022,"local_authorities":350,"hh_meters":314571,"hh_twh":124.246,"mean_gwh_per_hh_meter":0.395,"unallocated_hh_meters":2829,"unallocated_hh_twh":2.6763,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2023,"local_authorities":350,"hh_meters":313550,"hh_twh":121.38,"mean_gwh_per_hh_meter":0.3871,"unallocated_hh_meters":2835,"unallocated_hh_twh":2.6307,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"},{"year":2024,"local_authorities":350,"hh_meters":386961,"hh_twh":121.522,"mean_gwh_per_hh_meter":0.314,"unallocated_hh_meters":4132,"unallocated_hh_twh":2.6826,"geography_basis":"2021 (England and Wales) and 2022 (Scotland) geographies"}],"slough_series":[{"year":2010,"hh_meters":347,"hh_twh":0.5828,"mean_gwh_per_hh_meter":1.6797,"all_non_domestic_gwh":null,"all_meter_gwh":null},{"year":2011,"hh_meters":356,"hh_twh":0.6311,"mean_gwh_per_hh_meter":1.7726,"all_non_domestic_gwh":null,"all_meter_gwh":null},{"year":2012,"hh_meters":365,"hh_twh":0.6884,"mean_gwh_per_hh_meter":1.8859,"all_non_domestic_gwh":812.3,"all_meter_gwh":1013.2},{"year":2013,"hh_meters":383,"hh_twh":0.723,"mean_gwh_per_hh_meter":1.8878,"all_non_domestic_gwh":838.8,"all_meter_gwh":1037.6},{"year":2014,"hh_meters":460,"hh_twh":0.753,"mean_gwh_per_hh_meter":1.637,"all_non_domestic_gwh":870.3,"all_meter_gwh":1071.2},{"year":2015,"hh_meters":401,"hh_twh":0.778,"mean_gwh_per_hh_meter":1.94,"all_non_domestic_gwh":887.9,"all_meter_gwh":1088.6},{"year":2016,"hh_meters":643,"hh_twh":0.8403,"mean_gwh_per_hh_meter":1.3069,"all_non_domestic_gwh":920.3,"all_meter_gwh":1120.3},{"year":2017,"hh_meters":793,"hh_twh":0.9231,"mean_gwh_per_hh_meter":1.164,"all_non_domestic_gwh":988,"all_meter_gwh":1185.7},{"year":2018,"hh_meters":817,"hh_twh":1.0032,"mean_gwh_per_hh_meter":1.2279,"all_non_domestic_gwh":1063.9,"all_meter_gwh":1259.8},{"year":2019,"hh_meters":822,"hh_twh":1.0841,"mean_gwh_per_hh_meter":1.3189,"all_non_domestic_gwh":1142.3,"all_meter_gwh":1338.6},{"year":2020,"hh_meters":822,"hh_twh":1.1394,"mean_gwh_per_hh_meter":1.3862,"all_non_domestic_gwh":1189.9,"all_meter_gwh":1395.6},{"year":2021,"hh_meters":830,"hh_twh":1.2665,"mean_gwh_per_hh_meter":1.5259,"all_non_domestic_gwh":1324.1,"all_meter_gwh":1521.4},{"year":2022,"hh_meters":856,"hh_twh":1.4077,"mean_gwh_per_hh_meter":1.6445,"all_non_domestic_gwh":1462.6,"all_meter_gwh":1649.4},{"year":2023,"hh_meters":841,"hh_twh":1.5679,"mean_gwh_per_hh_meter":1.8643,"all_non_domestic_gwh":1622.3,"all_meter_gwh":1814.1},{"year":2024,"hh_meters":918,"hh_twh":1.7343,"mean_gwh_per_hh_meter":1.8892,"all_non_domestic_gwh":1786.3,"all_meter_gwh":1984.9}],"intensity_top_20":[{"rank":1,"name":"Slough","code":"E06000039","mean_gwh_per_meter_2013":1.8878,"mean_gwh_per_meter_2024":1.8892,"ratio":1.0008,"hh_meters_2013":383,"hh_meters_2024":918},{"rank":2,"name":"Hart","code":"E07000089","mean_gwh_per_meter_2013":0.6385,"mean_gwh_per_meter_2024":0.3973,"ratio":0.6222,"hh_meters_2013":170,"hh_meters_2024":627},{"rank":3,"name":"Hillingdon","code":"E09000017","mean_gwh_per_meter_2013":1.5137,"mean_gwh_per_meter_2024":0.8595,"ratio":0.5678,"hh_meters_2013":601,"hh_meters_2024":1627},{"rank":4,"name":"Tower Hamlets","code":"E09000030","mean_gwh_per_meter_2013":1.0414,"mean_gwh_per_meter_2024":0.5822,"ratio":0.5591,"hh_meters_2013":1991,"hh_meters_2024":2978},{"rank":5,"name":"Dacorum","code":"E07000096","mean_gwh_per_meter_2013":0.8381,"mean_gwh_per_meter_2024":0.4657,"ratio":0.5557,"hh_meters_2013":270,"hh_meters_2024":913},{"rank":6,"name":"City of London","code":"E09000001","mean_gwh_per_meter_2013":1.3228,"mean_gwh_per_meter_2024":0.6993,"ratio":0.5286,"hh_meters_2013":1647,"hh_meters_2024":2083},{"rank":7,"name":"Argyll and Bute","code":"S12000035","mean_gwh_per_meter_2013":0.4192,"mean_gwh_per_meter_2024":0.2184,"ratio":0.521,"hh_meters_2013":255,"hh_meters_2024":628},{"rank":8,"name":"Westminster","code":"E09000033","mean_gwh_per_meter_2013":0.7899,"mean_gwh_per_meter_2024":0.4023,"ratio":0.5093,"hh_meters_2013":3172,"hh_meters_2024":5683},{"rank":9,"name":"Camden","code":"E09000007","mean_gwh_per_meter_2013":0.8274,"mean_gwh_per_meter_2024":0.3874,"ratio":0.4682,"hh_meters_2013":1187,"hh_meters_2024":2326},{"rank":10,"name":"Greenwich","code":"E09000011","mean_gwh_per_meter_2013":0.5809,"mean_gwh_per_meter_2024":0.2659,"ratio":0.4578,"hh_meters_2013":485,"hh_meters_2024":1238},{"rank":11,"name":"North Warwickshire","code":"E07000218","mean_gwh_per_meter_2013":1.5528,"mean_gwh_per_meter_2024":0.6984,"ratio":0.4498,"hh_meters_2013":212,"hh_meters_2024":544},{"rank":12,"name":"Derby","code":"E06000015","mean_gwh_per_meter_2013":0.8275,"mean_gwh_per_meter_2024":0.3694,"ratio":0.4464,"hh_meters_2013":500,"hh_meters_2024":1331},{"rank":13,"name":"East Lindsey","code":"E07000137","mean_gwh_per_meter_2013":0.7228,"mean_gwh_per_meter_2024":0.3211,"ratio":0.4443,"hh_meters_2013":329,"hh_meters_2024":972},{"rank":14,"name":"Newport / Casnewydd","code":"W06000022","mean_gwh_per_meter_2013":1.8494,"mean_gwh_per_meter_2024":0.8198,"ratio":0.4433,"hh_meters_2013":307,"hh_meters_2024":882},{"rank":15,"name":"Burnley","code":"E07000117","mean_gwh_per_meter_2013":0.7756,"mean_gwh_per_meter_2024":0.3437,"ratio":0.4431,"hh_meters_2013":176,"hh_meters_2024":447},{"rank":16,"name":"Bolsover","code":"E07000033","mean_gwh_per_meter_2013":1.1524,"mean_gwh_per_meter_2024":0.5105,"ratio":0.443,"hh_meters_2013":150,"hh_meters_2024":369},{"rank":17,"name":"Cambridge","code":"E07000008","mean_gwh_per_meter_2013":0.9911,"mean_gwh_per_meter_2024":0.437,"ratio":0.4409,"hh_meters_2013":424,"hh_meters_2024":1138},{"rank":18,"name":"Nottingham","code":"E06000018","mean_gwh_per_meter_2013":0.6765,"mean_gwh_per_meter_2024":0.2971,"ratio":0.4392,"hh_meters_2013":799,"hh_meters_2024":1778},{"rank":19,"name":"Wandsworth","code":"E09000032","mean_gwh_per_meter_2013":0.5134,"mean_gwh_per_meter_2024":0.2255,"ratio":0.4392,"hh_meters_2013":477,"hh_meters_2024":1441},{"rank":20,"name":"Welwyn Hatfield","code":"E07000241","mean_gwh_per_meter_2013":1.3909,"mean_gwh_per_meter_2024":0.5932,"ratio":0.4265,"hh_meters_2013":264,"hh_meters_2024":680}],"top_risers_2019_2023":[{"rank_on_half_hourly":1,"rank_on_all_non_domestic":1,"code":"E06000039","name":"Slough","region":"South East","hh_change_gwh":483.7,"hh_share_of_hh_growth_pct":44.22,"all_non_domestic_change_gwh":480,"all_non_domestic_share_of_that_growth_pct":50.97,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.01},{"rank_on_half_hourly":2,"rank_on_all_non_domestic":2,"code":"E09000017","name":"Hillingdon","region":"Outer London","hh_change_gwh":196.1,"hh_share_of_hh_growth_pct":17.93,"all_non_domestic_change_gwh":183.3,"all_non_domestic_share_of_that_growth_pct":19.46,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":3,"rank_on_all_non_domestic":3,"code":"E07000096","name":"Dacorum","region":"East","hh_change_gwh":91.1,"hh_share_of_hh_growth_pct":8.32,"all_non_domestic_change_gwh":85,"all_non_domestic_share_of_that_growth_pct":9.02,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":4,"rank_on_all_non_domestic":4,"code":"W06000022","name":"Newport / Casnewydd","region":"Wales","hh_change_gwh":65.3,"hh_share_of_hh_growth_pct":5.97,"all_non_domestic_change_gwh":60.7,"all_non_domestic_share_of_that_growth_pct":6.45,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.07},{"rank_on_half_hourly":5,"rank_on_all_non_domestic":6,"code":"E06000054","name":"Wiltshire","region":"South West","hh_change_gwh":57.3,"hh_share_of_hh_growth_pct":5.24,"all_non_domestic_change_gwh":21.5,"all_non_domestic_share_of_that_growth_pct":2.28,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":2.66},{"rank_on_half_hourly":6,"rank_on_all_non_domestic":5,"code":"E07000102","name":"Three Rivers","region":"East","hh_change_gwh":56,"hh_share_of_hh_growth_pct":5.12,"all_non_domestic_change_gwh":50.6,"all_non_domestic_share_of_that_growth_pct":5.37,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.11},{"rank_on_half_hourly":7,"rank_on_all_non_domestic":7,"code":"E09000009","name":"Ealing","region":"Outer London","hh_change_gwh":32.7,"hh_share_of_hh_growth_pct":2.99,"all_non_domestic_change_gwh":16,"all_non_domestic_share_of_that_growth_pct":1.7,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":2.04},{"rank_on_half_hourly":8,"rank_on_all_non_domestic":8,"code":"E07000073","name":"Harlow","region":"East","hh_change_gwh":19.9,"hh_share_of_hh_growth_pct":1.82,"all_non_domestic_change_gwh":15.1,"all_non_domestic_share_of_that_growth_pct":1.6,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.32},{"rank_on_half_hourly":9,"rank_on_all_non_domestic":9,"code":"E07000089","name":"Hart","region":"South East","hh_change_gwh":17.9,"hh_share_of_hh_growth_pct":1.64,"all_non_domestic_change_gwh":13.8,"all_non_domestic_share_of_that_growth_pct":1.47,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.3},{"rank_on_half_hourly":10,"rank_on_all_non_domestic":10,"code":"E07000218","name":"North Warwickshire","region":"West Midlands","hh_change_gwh":14.8,"hh_share_of_hh_growth_pct":1.36,"all_non_domestic_change_gwh":7.5,"all_non_domestic_share_of_that_growth_pct":0.79,"up_on_both_series":true,"divergence_ratio_hh_over_all_non_domestic":1.98}],"data_centre_overlay_2024":[{"area":"Great Britain","is_local_authority":false,"code":null,"year":2024,"data_centre_sites":239,"data_centre_twh":4.4595,"desnz_share_of_all_electricity_pct":1.79,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":39.1,"all_meter_twh_implied":249.2477,"large_site_twh":121.522,"share_of_large_site_electricity_pct":3.67,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 121.5220 TWh","percentage_point_difference":1.88,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Hillingdon","is_local_authority":true,"code":"E09000017","year":2024,"data_centre_sites":10,"data_centre_twh":0.5363,"desnz_share_of_all_electricity_pct":28.13,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":21.5,"all_meter_twh_implied":1.9065,"large_site_twh":1.3983,"share_of_large_site_electricity_pct":38.35,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.3983 TWh","percentage_point_difference":10.22,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Slough","is_local_authority":true,"code":"E06000039","year":2024,"data_centre_sites":30,"data_centre_twh":1.2934,"desnz_share_of_all_electricity_pct":65.16,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":10,"all_meter_twh_implied":1.9849,"large_site_twh":1.7343,"share_of_large_site_electricity_pct":74.58,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7343 TWh","percentage_point_difference":9.42,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."},{"area":"Tower Hamlets","is_local_authority":true,"code":"E09000030","year":2024,"data_centre_sites":29,"data_centre_twh":0.4299,"desnz_share_of_all_electricity_pct":18.25,"desnz_denominator":"all electricity taken from the grid, domestic and non-domestic","domestic_share_of_all_electricity_pct":18.4,"all_meter_twh_implied":2.3562,"large_site_twh":1.7339,"share_of_large_site_electricity_pct":24.79,"large_site_denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7339 TWh","percentage_point_difference":6.55,"approximation_label":"Approximation. The numerator is an all-meter figure and the denominator is a half-hourly one, and the two cover slightly different twelve-month periods."}],"data_centre_great_britain_series":[{"year":2020,"data_centre_sites":221,"data_centre_twh":3.1589,"desnz_share_of_all_electricity_pct":1.229,"large_site_twh":118.968,"share_of_large_site_electricity_pct":2.655},{"year":2021,"data_centre_sites":224,"data_centre_twh":3.4448,"desnz_share_of_all_electricity_pct":1.332,"large_site_twh":122.904,"share_of_large_site_electricity_pct":2.803},{"year":2022,"data_centre_sites":230,"data_centre_twh":3.8433,"desnz_share_of_all_electricity_pct":1.539,"large_site_twh":124.246,"share_of_large_site_electricity_pct":3.093},{"year":2023,"data_centre_sites":238,"data_centre_twh":4.1268,"desnz_share_of_all_electricity_pct":1.658,"large_site_twh":121.38,"share_of_large_site_electricity_pct":3.4},{"year":2024,"data_centre_sites":239,"data_centre_twh":4.4595,"desnz_share_of_all_electricity_pct":1.789,"large_site_twh":121.522,"share_of_large_site_electricity_pct":3.67}],"intensity_distribution":{"n":325,"deciles":[0.2216,0.2414,0.2587,0.2746,0.2914,0.3072,0.3298,0.3505,0.3891],"n_at_or_above_half":8,"n_below_a_fifth":11}},"verification":{"how_to_verify":"Re-download the four DESNZ files, check the md5s in the source list, parse them independently and recompute each figure below. Any mismatch should block release.","recompute_from_the_published_csv":[{"check":"Population size","expected":378,"recipe":"Count data rows in the CSV."},{"check":"Intensity base size, reconciled basis","expected":325,"recipe":"Count rows with in_intensity_base_reconciled = 1."},{"check":"Intensity base size, published-name basis","expected":303,"recipe":"Count rows with in_intensity_base_published_name = 1."},{"check":"Intensity base size, published-code basis","expected":323,"recipe":"Count rows with in_intensity_base_published_code = 1."},{"check":"Local authorities at or above parity, 2013 to 2024","expected":1,"expected_names":["Slough"],"recipe":"Count rows with in_intensity_base_reconciled = 1 and intensity_ratio_2013_2024 >= 1."},{"check":"Median intensity ratio, 2013 to 2024","expected":0.2914,"tolerance":0.0001,"recipe":"Median of intensity_ratio_2013_2024 where in_intensity_base_reconciled = 1."},{"check":"Slough mean GWh per half-hourly meter, 2013 and 2024","expected":[1.8878,1.8892],"recipe":"The Slough row: hh_mean_gwh_per_meter_2013 and hh_mean_gwh_per_meter_2024."},{"check":"Direction of change 2019 to 2023, half-hourly","expected":{"down":326,"up":24,"n":350},"recipe":"Count hh_direction_2019_2023."},{"check":"Top ten share of half-hourly growth, 2019 to 2023","expected":94.6,"tolerance":0.05,"denominator":1093.9,"recipe":"Sum the ten largest positive hh_gwh_change_2019_2023, divide by the sum of all positive values, times 100."},{"check":"Direction of change 2019 to 2023, all non-domestic","expected":{"down":337,"up":13,"n":350},"recipe":"Count all_non_domestic_direction_2019_2023."},{"check":"Top ten share of all-non-domestic growth, 2019 to 2023","expected":99.13,"tolerance":0.05,"denominator":941.7,"recipe":"Sum the ten largest positive all_non_domestic_gwh_change_2019_2023, divide by the sum of all positive values, times 100."},{"check":"The two top-ten sets are the same ten authorities","expected":true,"recipe":"Compare the sets of rows with hh_riser_rank_2019_2023 <= 10 and all_non_domestic_riser_rank_2019_2023 <= 10."},{"check":"All ten top risers are up on both series","expected":true,"recipe":"For those ten rows, up_on_both_series_2019_2023 = 1."},{"check":"Great Britain large-site electricity, 2024","expected":121.522,"unit":"TWh","tolerance":0.001,"recipe":"Sum hh_gwh_2024 over all rows, divide by 1,000. Excludes the Unallocated row, which is not in the CSV."},{"check":"Data centres as a share of GB large-site electricity, 2024","expected":3.67,"tolerance":0.01,"denominator":"half-hourly (large-site) electricity in the same area in 2024, 121.5220 TWh","recipe":"4.4595 TWh divided by the previous check, times 100."},{"check":"Data centres as a share of Slough large-site electricity, 2024","expected":74.58,"tolerance":0.01,"denominator":"half-hourly (large-site) electricity in the same area in 2024, 1.7343 TWh","recipe":"The Slough row: data_centre_twh_2024 divided by hh_gwh_2024 / 1,000, times 100."},{"check":"Clean-window parity count, 2019 to 2023","expected":6,"expected_names":["Slough","Three Rivers","Dacorum","Hillingdon","Harlow","Newport / Casnewydd"],"recipe":"Count rows with intensity_ratio_2019_2023_clean_window >= 1."}],"recompute_from_the_source_workbooks":[{"check":"DESNZ data-centre share reconciles to the subnational all-meter total, Great Britain 2024","recipe":"4.459538 TWh divided by 0.01789199 should equal the subnational Great Britain all-meter total.","expected":249.2477,"tolerance":0.001,"why":"It proves DESNZ's published share uses an all-electricity denominator including homes, which is the premise of the third metric."},{"check":"The same reconciliation for Slough","recipe":"1.293443 TWh divided by 0.65164182 should equal Slough's subnational all-meter total.","expected":1.9849,"tolerance":0.001},{"check":"Great Britain 2024 all-meter and all-non-domestic totals","expected":{"all_meter_twh":249.248,"all_non_domestic_twh":151.744},"tolerance":0.001,"recipe":"Sum the subnational workbook's Great Britain row for 2024."},{"check":"Half-hourly panel shape","expected":{"total_rows":5369,"la_year_observations":5354,"unallocated_rows":15,"hh_meters_2024":386961,"hh_twh_2024":121.522},"recipe":"Count and sum the half-hourly rows of the MSOA workbook, 2010 to 2024."},{"check":"The published mean equals total kWh divided by meters on every local authority row","expected":0,"unit":"mismatches","recipe":"For all 5354 local authority rows, compare hh_mean_kwh_per_meter with hh_kwh / hh_meters."},{"check":"The 2024 reclassification break is in the source, not in our arithmetic","expected":{"hh_meters_2023":313550,"hh_meters_2024":386961,"change_pct":23.41},"recipe":"Compare half-hourly meter counts in the MSOA workbook for 2023 and 2024."}],"things_a_checker_should_not_be_surprised_by":["The intensity base is 325, not the 303 the brief expected. 303 is what literal name matching gives; it drops twenty-two Welsh authorities over a bilingual spelling change. Both figures are in the JSON.","The 2024 break is not attributed to MHHS anywhere, because MHHS migration starts in late October 2025.","Half-hourly and non-half-hourly figures are never added. Any check that adds them will not reconcile.","The Unallocated row is excluded from the published CSV and from every total. It is reported separately in the JSON.","Re-extracting the DESNZ special article PDF will produce '2423' and '2594' where the source means 242 and 259 with footnote markers attached.","The published CSV rounds GWh to one decimal place, so a share recomputed from it can differ from the figure in this JSON in the last decimal. The top-ten share of half-hourly growth is 94.60 per cent at full precision and 94.61 per cent recomputed from the rounded column. Tolerances above allow for that; the full-precision figures come from the panels in data/research/uk-large-site-electricity-data-centres-2026/."]},"dataset":{"csv":"/research/uk-large-site-electricity-data-centres-2026.csv","readme":"/research/uk-large-site-electricity-data-centres-2026-README.txt","rows":378,"columns":47,"unit":"one local authority","licence":"Open Government Licence v3.0","attribution":"Contains public sector information licensed under the Open Government Licence v3.0.","derived_licence":"Creative Commons Attribution 4.0 International (CC BY 4.0)","derived_licence_url":"https://creativecommons.org/licenses/by/4.0/","derived_attribution":"Servnet, One of 325 local authorities has an average half-hourly meter as big as it was in 2013: Slough, https://www.servnetuk.com/research/uk-large-site-electricity-data-centres-2026","excludes":"The Unallocated row, which is not a local authority.","csv_sha256":"9d1c3f5fc1753eee2ba631d6ffd719f8372fcb4eef7cc45cda4a161bf4596862","readme_sha256":"3102f0c43c67541534c89abdf0923de2f05feff45ca3b0417dcbc2d8990d190e"}}