Server power consumption calculator

Less than its power supplies are rated for — which is why most answers online are wrong. A supply rating is a ceiling, not a draw: a 2U server with two 1,400 W supplies in 1+1 redundancy has one supply live and can demand up to 1,400 W, but a consolidated hypervisor typically runs at 35–55% of that. This calculator separates the two: provisioned power (a fact, from the vendor document) and an operating estimate (your load factor, labelled as an estimate). Nobody publishes a draw figure per configuration, so we do not invent one.

Take the provisioned load of everything in the rack and divide by the supply voltage: at 230 V single phase, 7 kW is about 30 A; the same load on a 400 V three-phase feed is about 10 A per phase. The calculator shows the design current for both, and the next standard protective-device size above it. Sizing the circuit on an average draw rather than the provisioned load is how racks end up tripping under load.

Not automatically — BS 7671 contains no blanket 80% derating rule for final circuits, and repeating that rule of thumb as if it were a regulation is a common mistake. What matters is the design current, the protective device characteristic, cable rating, grouping, ambient temperature and installation method. We give your electrician the design current; they size the installation to BS 7671.

Power Usage Effectiveness is total facility energy divided by IT energy: PUE 1.0 would mean every watt reaches the kit and none is spent on cooling. A UK enterprise server room typically runs 1.3–1.6; a well-operated colocation hall is nearer 1.15–1.25. Setting PUE to 1.0 in this tool gives the IT load alone, which is the figure to compare against a colocation quote that bills IT power separately.

Effectively all the electricity it consumes, because a server does no mechanical work — ASHRAE’s guidance treats heat output as equal to electrical input. So a rack drawing 6 kW is a 6 kW heat load, or about 20,500 BTU/hr, and the cooling has to remove it continuously. The calculator shows both units so you can hand the figure to whoever sizes the cooling.

Annual kWh multiplied by the UK government's published conversion factors for 2026: 0.13096 kg CO₂e per kWh for electricity generation (scope 2) and 0.01299 kg CO₂e per kWh for transmission and distribution losses (scope 3). Both are shown separately because SECR and most corporate reporting want them split. If you buy a renewable tariff your market-based scope 2 figure will differ — the location-based figure shown here is the one the conversion factors give.

From each model’s own manufacturer technical document — the same verified specification library behind our 108 data sheets and 229 comparison pages. For each model we hold the power supplies the vendor lists, how many the chassis takes, and the redundancy modes documented for it, so the provisioned figure is arithmetic on published facts rather than an estimate. Models whose supplies belong to an enclosure rather than the node (blades, multi-node trays) are excluded, because quoting a shelf’s rating as one server’s draw would be wrong.