The Main Differences Between Leased Line and EFM - A Quick Comparison

Ethernet First Mile (EFM) - is sometimes used as a relatively cheap, relatively quick-to-install alternative to fibre leased lines. However, there are some significant differences between EFM and leased line connections.

Ethernet Firrst Mile over Copper sends data using electrical signals rather light through fibre-optic cables. So fibre leased lines can carry more data.

Fibre Leased Line vs Uncontended EFM over Copper

    Geographic Availability

    Fibre leased lines are available far more widely. EFM coverage varies for each underlying wholesale network provider. The largest EFM network provider can serve 3035 of the UK's 5564 telephone exchange areas. The second-largest serves 898 of the 5564 exchanges. And even if you're in a coverage area, you're not guaranteed to get the top speeds often touted (e.g. 20Mbps for the largest network, and 35Mbps for the second biggest), at least using copper.

    Installation Lead Times

    EFM over copper is on average quicker to install than a fibre leased line, taking as little as 25 working days to install, compared to around 65 working days for a fibre leased line. That's mainly because it uses new phone lines running through existing telecoms ducts rather than requiring its own new ducts to be created. That said, it's not 25 working days, it's 'as little as' 25 days, i.e. in some telephone exchange areas, with some underlying providers it could take up to 90 days. So if you need a backup connection, and you've left ordering your fibre-leased line a bit late, it's often not a bad idea to install an EFM line while you wait for your fibre leased line to be installed.

    Speed Upgrade Options

    Broadly, EFM is less upgradeable. That's because providers use 2, 4, 6 or 8 pairs of copper wires, and once you use those up you've hit the limit of what you can get via EFM. In theory, you could another more EFM circuits and bond them to your original ones, but frankly, by then the costs tend to be higher than switching to a fibre leased line, so no-one does that. Fibre leased lines can often be upgraded to deliver speeds of 10,000Mbps, i.e. massively more than the puny 20Mbps or 35Mbps that EFM can offer if you're atypically close to your local telephone exchange and that exchange has the relevant EFM equipment.

    Speed Guarantees

    When you order a fibre leased line or an EFM over copper line, you should be told the minimum connection speed that's likely to be achieved. For a fibre leased line, this will be identical to whatever you think you're ordering. For an EFM one, you may get given a speed estimate for what you're likely to see, plus a lower speed estimate indicating the minimum connection speed you're likely to experience.


    EFM used to be cheaper than the equivalent fibre leased lines. But as fibre leased line prices fell, this isn't necessarily the case any more.

    Download Speed

    In theory, the biggest EFM network can deliver up to 20Mbps downstream, and one of its major rivals' network can deliver up to 35 Mbps downstream via copper. In practice, these speeds are exceptionally rare. Fibre leased lines, in comparison, can deliver 10,000 Mbps downstream, typically. For most UK business sites, the reality is more likely to be 10-12Mbps for EFM versus 10,000Mbps for a fibre leased line, with only budgetary considerations causing the fibre leased line speed choice to fall to something closer to that offered by EFM.

    Upload Speed

    Both EFM over copper and fibre leased lines are symmetrical, i.e. for each connection, the upload speed matches the download speed. Unfortunately for EFM that means the maximum upload speed is likely to be 20Mbps or 35Mbps in theory, and far less in practice, compared to up to 10,000 Mbps upstream for fibre leased lines.

    Connection Contention

    Fibre leased lines aren't contended. Some EFM circuits are contended.

    Typical Customer

    Fibre leased lines tend to be bought by businesses of all sizes, including SMEs. EFM circuits tend to be bought solely by SMEs, and by mid-sized businesses looking for a backup connection to their fibre leased line.

    Electrical Interference

    EFM over copper uses electrical signals that are sent over copper wires, whereas fibre leased lines send laser light over glass fibres. The former suffers greater distance-dependent signal degradation.


    EFM may be less reliable than a fibre leased line. Some EFM circuits plug into a single line card at the exchange, meaning there's a single point of failure there. Some EFM providers do not automatically exclude faulty copper pairs from their link, potentially leading to more stability issues. Some EFM Providers do not have fully residential backhaul from local telephone exchanges.

    Price Trends

    EFM prices are unlikely to fall much further. Fibre leased line prices are likely to continue to fall.

    Role in Mobile Backhaul

    EFM speeds are too low to make EFM useful for mobile network backhaul. Fibre leased lines, in contrasts, are routinely used in Mobile backhaul. This is one of the reasons mobile networks often end up merging with fixed-line networks (e.g. BT & EE, Virgin Media & O2, Cable & Wireless & Vodafone).

    Major Wholesale Suppliers

    Not all wholesale ethernet providers offer EFM. TalkTalk Business and BT Wholesale do offer it, however, Virgin Media, arguably the #2 for leased lines, doesn't offer EFM. Many retail leased line providers offer both fibre leased line and EFM options, building on the underlying connectivity provided by TalkTalk or BT.

Notes on the the above comparison

We've just compared dedicated fibre-optic leased lines against dedicated ethernet first mile over copper circuits, within the UK. Let's explain what that excludes.

It excludes from consideration some non-fibre leased lines that are delivered using dedicated EFM circuits. We're excluding that as there's no point comparing things that are identical.

We're excluding cases where EFM is delivered over fibre. Some but not all BT Wholesale EFM products are delivered over fibre. Again, it makes no sense to compare what is essentially a fibre leased line with a fibre leased line. Note that BT Wholesale isn't the only wholesale provider around.

Finally, not all EFM circuits are dedicated, i.e. some have to share a limited amount of backhaul bandwidth with other subscribers. We're not comparing these, as frankly these contended EFM circuits aren't particularly popular and many ISPs don't even offer contended EFM.

We compare leased line costs for your specific location, making the big network operators fight each other to provide the underlying connectivity.

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