Upgrading your business internet throws up two serious options that look similar on a price comparison and behave completely differently in real life: full-fibre broadband (FTTP) and a leased line. One can be ten times cheaper than the other for headline speed - and yet the dearer one is sometimes the obvious right call. The difference is not really about speed at all. It is about guarantees, and what your business loses every hour it is offline.
What each one actually is
FTTP - Fibre to the Premises - is full-fibre broadband: a fibre cable running all the way to your building, with no old copper in the last stretch. It is fast, increasingly available, and relatively cheap. Our guide to business broadband covers where it fits.
A leased line is a dedicated fibre connection reserved entirely for your business, from your premises to the provider's network. Nobody else shares it. It costs considerably more, often takes longer to install, and on paper its speed may look no higher than good FTTP. The value is in what you cannot see on the speed figure.
Shared vs dedicated: the heart of it
This is the single most important distinction, and it explains the price gap. FTTP is a contended (shared) service: the fibre to your area is shared among many businesses and homes, so your real-world speed can dip when everyone is online - the classic evening or Monday-morning slowdown. For most uses, it is still excellent.
A leased line is uncontended: the bandwidth is yours alone, all day, every day, with nobody to compete with. That is why a leased line feels rock-steady under load when a shared line wobbles. If you have ever wondered why two connections with the same headline speed feel so different, contention is usually the answer - and it connects directly to the difference between bandwidth, throughput and latency.
Symmetry: the upload nobody mentions
Most FTTP packages are asymmetric: fast download, much slower upload. That is fine for browsing and streaming, but it bites the moment your business sends data out - uploading large files to clients, hosting anything on-site, backing up to the cloud, or running lots of video calls where everyone is transmitting at once.
Leased lines are symmetric: upload speed matches download. For a firm that pushes data out as much as it pulls it in - design studios, media, anyone backing up large volumes off-site, or running their own servers - that symmetry is often the real reason to pay for a leased line, quite apart from contention.
- •FTTP: usually fast down, slower up - great for consuming, weaker for sending.
- •Leased line: equal up and down - built for businesses that transmit, host or back up heavily.
- •If your pain is slow uploads, more download speed on FTTP will not fix it.
The SLA: what you are really paying for
The biggest difference is not in the technology but in the promise behind it. FTTP is typically a best-efforts consumer-grade service: if it breaks, it is fixed when an engineer is available, often measured in days, with no compensation that matters.
A leased line comes with a business-grade SLA - a Service Level Agreement - guaranteeing uptime (commonly 99.9% or better) and, crucially, a fast fix time, often same-day, with money back if they miss it. You are buying a contractual promise, not just a connection. If you do not yet know what those guarantees mean in practice, what is an SLA is worth five minutes. For a business that simply cannot trade when the internet is down, that promise is the entire point.
So which should you choose?
Frame it around cost of downtime, not cost of the line. Work out what one day - or one hour - offline actually costs your business in lost orders, idle staff and missed deadlines. Compare that to the monthly difference between FTTP and a leased line, and the decision usually makes itself.
Choose FTTP if you are a smaller office, mainly consuming cloud services, and an occasional outage is survivable - it is superb value for that. Choose a leased line if downtime is genuinely costly, you rely on guaranteed performance, you upload heavily, or you host services that must always be reachable. A common, sensible pattern is a leased line as the primary connection with FTTP as an automatic backup - the kind of resilient setup that pairs well with SD-WAN and the wider network design. Browse the full range of business options on our solutions hub.