12 Differences Between G.Fast and Leased Lines - A Quick Comparison

G.Fast could deliver fast speeds to much of the country, but is losing out to full-fibre broadband.

Leased Line vs G.Fast

You've probably heard of ADSL and FTTC, and perhaps even EFM. What they all have in common is that they allow data to be sent over wires, like the sort used to carry traditional phone calls, at least for the bit of the journey closest to your property. However, there's another faster option called G.FAST which many people haven't heard about yet.

However, The G.FAST's rollout plan has been repeatedly revised in the light of BT coming under political pressure to invest in full-fibre networks instead of sweating its legacy copper network for a few more years with technologies like G.FAST. Openreach's coverage target for G.FAST was cut from 10 million premises to 5.7 million to 2.73 million by March 2020.

After some initial trials, the service was due to go live in April 2020, but the coronavirus pandemic caused most installations to be put on ice.


    G.FAST is available to approximately 2.7 million UK premises i.e. about 10% of sites, mainly residential addresses. Leased lines, in contrast, are available to order at pretty much every UK premise.


    G.FAST is considerably cheaper than getting a leased line, but you're not really comparing like with like.

    Download Speed

    - Leased lines can offer fixed downstream connection speeds of up to 10 Gbps. G.FAST offers far slower speeds, e.g. Openreach planned to offer a top speed of 330 Mbps, i.e. 97% slower than 10 Gbps. Some providers have opted to offer G.FAST download speeds of 160Mbps or less.

    Upload Speed

    Leased lines can offer fixed upstream speeds of up to 10Gbps. Openreach planned to offer a top upload speed of 50Mbps, i.e. 200 times slower than a 10 Gbps leased line.

    Connection Contention

    Leased lines aren't contended. G.FAST is contended. With G.FAST, you have to share a pool of backhaul bandwidth with other subscribers and if too many people max out their connections at once, your throughput falls. With a leased line, the backhaul bandwidth is reserved solely for your use.

    Target Market

    In theory, leased lines are aimed at businesses, and G.FAST is aimed at residential properties, and businesses.

    Copper v Fibre

    Leased lines delivering 40Mbps or more use fibre-optic cables for the whole journey. Like FTTC, G.FAST always uses copper cables for the part of the journey closest to you, before switching the signal over to fibre-optic cables at cabinets some distance away.

    Dominant Suppliers

    There's just one major G.FAST network in the UK - that of BT's infrastructure subsidiary Openreach, so pretty much all G.FAST services you will come across are based on an ISP providing services (Internet access, IP addressing, Wi-Fi routers, support etc) on top of that. With leased lines, there are several different competing physical networks, including Virgin Media's in a majority of the country, and Colt, KCOM and SSE Telecom in a more limited number of locations. With leased lines, there are many other providers what can combine a local 'tail' circuit from Openreach or Virgin Media with their network to create a leased line that's not solely dependent on Openreach infrastructure.


    G.FAST connections tend to come with data transfer quotas. Leased lines tend to be unmetered, i.e. you can send and receive as much data as you like, all the time, without incurring extra usage fees or a usage cap.

    Electrical Interference

    G.FAST connections use electrical signals for the first part of the journey, closest to you, as unlike mid-to-high-bandwidth leased lines, they don't use fibre-optic circuits for that bit.


    G.FAST connections that deliver 330Mbps downstream and 50Mbps upstream aren't likely to be upgradable. Leased lines can usually be upgraded to deliver higher connection speeds, though sometimes that will require the installation of a new leased line circuit.

    Long Term Future

    Leased lines are likely to continue to be around for decades. G.FAST is likely to only have a comparatively short future, as the plans to switch off the UK's main legacy phone network in 2025 mean the copper network upon which G.FAST operates is going to be retired once FTTP can take its place.

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