Leased line or FTTP, and when the difference matters

What you are actually buying

Almost every conversation about this starts with speed, and speed is the least important difference between the two. A business FTTP connection and a leased line can both give you a gigabit. What you are paying the difference for is not the number, it is the promise attached to it.

FTTP is a shared product sold on a best-efforts basis. The capacity in your area is shared with everyone else on it, the upload is usually slower than the download, and if it breaks the provider will fix it as soon as they reasonably can.

A leased line is a dedicated circuit. The bandwidth is yours whether or not anybody else is using theirs, the upload matches the download, and if it breaks there is a number in the contract saying how long they have to fix it before they start paying you.

What contention actually means

Contention gets explained badly, usually with a motorway metaphor that leaves people more confused than they started. In practice it means this: the capacity between your street and the wider internet is shared, and the provider has sold more of it than exists on the assumption that not everybody uses it at once.

That assumption is almost always correct, which is why contention is rarely the thing that catches a business out. Modern FTTP networks are generously provisioned and most offices never notice. If you are going to have a problem it will show up at the same time every day, usually mid-afternoon, and it will affect uploads before downloads.

The place it genuinely bites is uploads, and the businesses that feel it are the ones pushing data out rather than pulling it in: anybody backing up offsite during the working day, running a lot of video calls at once, or hosting something that customers connect into. A connection advertised as 900 down and 110 up is a different product from one that is 900 both ways, and the brochure rarely makes that obvious.

The fix time is the real difference

This is the part worth paying attention to, and it is almost never what the sales conversation is about.

A business FTTP fault is typically repaired on a next working day target, with an availability figure around 99.9%. That sounds like almost nothing until you convert it: 99.9% allows roughly eight and three quarter hours of downtime a year, and "next working day" on a Friday evening can mean Monday morning.

A leased line normally carries a two hour response and a four to six hour fix target, with availability around 99.95%, which is about four and a half hours a year. Premium service levels tighten that to a one hour response and an engineer on site within two to four hours, and typically cost ten to fifteen per cent more than the standard version.

So the honest comparison is not gigabit against gigabit. It is "somebody will look at it tomorrow" against "somebody is contractually on their way". For an office that can work offline for a morning, the first is fine and the second is money wasted. For a business that stops trading the moment the line drops, it is the other way round.

What it costs, and the charge nobody warns you about

Checked in October 2026, a business FTTP connection in the 500Mbps range runs roughly £60 to £100 a month on a twelve to twenty four month term, with installation free or close to it.

Leased line quotes gathered across the UK over the same period put the median at around £287 a month for 100Mbps and £319 for a gigabit, on standard thirty six month terms. Keener pricing exists in well served postcodes, starting nearer £69 and £129 respectively, and quotes vary far more than FTTP does because the cost is the circuit rather than the bandwidth.

That last point is worth acting on. Because you are paying for a dedicated circuit rather than for capacity, a hundred megabit leased line and a gigabit leased line cost almost the same. If you have decided you need one, buying the slow one to save money is the wrong economy.

The charge that catches people out is the excess construction charge. If the fibre does not already reach your building, somebody has to dig, and that cost is passed to you. Median excess construction charges over the same period came out around £2,200, with the middle half of quotes between roughly £350 and £7,400, and about one quote in ten above £16,000.

The lead time decides more than people expect

A business FTTP install where the infrastructure is already there is usually a couple of weeks to a month. A leased line is not.

Gigabit circuits ordered across the UK between 2023 and 2025 took a median of seventy eight days from order to live, which is about eleven weeks. Anything above a gigabit ran to roughly thirteen. That is the median, so half took longer, and the ones that take longer are generally the ones that needed digging.

This quietly settles a lot of arguments. If you are opening a second site in six weeks, a leased line is not an option for the opening, whatever anybody tells you. The realistic answer is FTTP with a 4G backup on day one and a leased line ordered in parallel if you still want it, which is a perfectly sensible thing to do and rarely gets suggested because it involves admitting the first option is a stopgap.

How to decide, in four questions

Could you trade for a day without it? If yes, FTTP is almost certainly right and the rest of this is an expensive answer to a question you do not have.

Does anything customer-facing live on your own premises, or do you push large amounts of data out during the day? If so the upload speed and the contention matter, and a symmetric connection earns its money.

Would four hours offline cost you more than the annual difference? That difference is roughly two and a half to three thousand pounds a year at current prices. Put a number on a lost half day and compare the two honestly, including the staff who cannot work rather than only the sales you miss.

When do you need it? If the answer is sooner than three months, the decision has been made for you, and the sensible move is to put FTTP in now and order the leased line afterwards if the numbers still say so.