This guide is written for owners and office managers, not network engineers. Prices were checked in November 2026. Business prices are normally quoted excluding VAT; confirm with the supplier.

For the basics of what a backup is and why lines fail, see the complete guide to broadband backup.

What an hour offline costs your business

Use this formula:

Hourly cost of downtime = (number of people who cannot work × their hourly cost to you) + (sales you cannot take per hour) + (cost of catching up afterwards)

Count the fully loaded cost of staff, not only wages: employer's National Insurance, pension contributions and overheads. Count only sales that are lost, not those that are merely delayed. Then add a note for what you cannot price, such as missed calls from new customers.

Two illustrations show how different the answers can be. The numbers are invented for the example; replace them with your own.

  • An eight-person office where six people cannot work without cloud systems, at a loaded cost of £25 an hour each, loses £150 an hour in paid idle time. A four-hour outage costs £600 before anyone counts the late client work.
  • A shop or café that takes £300 an hour, mostly by card, and has no offline card mode, loses most of that £300 an hour for as long as the terminal is down, at the busiest time of day if it is unlucky.

For a benchmark, a 2024 report by the business provider Beaming, based on a Censuswide survey of 504 UK businesses, estimated that firms lost 50.5 million hours and £3.7 billion to internet failures in 2023. In the business-services sector it found an average of 2.9 outages per business, 10.6 hours of disruption in total, and a median cost of £600 2. The report was commissioned by a company that sells connectivity, so treat it as indicative.

Now set your hourly figure against what cover costs.

Annual cost of coverHours of avoided downtime needed to pay for it, at £50 an hourAt £150 an hourAt £500 an hour
£96 a year: a provider 4G add-on at £8 a month ex VAT 71.9 hours0.6 hours0.2 hours
£2,400 a year: a leased line at £200 a month 548 hours16 hours4.8 hours

The table makes the usual case plain. Mobile failover pays for itself with a single short outage. A leased line has to be justified by more than outage avoidance, typically by guaranteed speed in both directions and a contractual fix time.

Why compensation will not cover you

Ofcom's automatic compensation scheme pays £10.34 a day when a total loss of service is not fixed after two full working days. It is described as covering residential fixed broadband and landline products 1. If your business has a business contract, the scheme does not apply to you.

What you have instead is your contract. Two terms matter:

  • SLA (service level agreement): the supplier's written promise about availability, response and repair times.
  • Service credit: the refund or bill credit you receive if the supplier misses that promise.

Read what the credit is worth. Two published examples give the scale. BT Business offers a one-time £60 credit if its 4G backup fails to activate within 30 minutes of you reporting a fixed-line fault 8. Sky Business has advertised a one-off £25 credit if its 4G backup does not activate within 30 seconds of a reported outage, with eligibility depending on the package; check the current terms for yours 9. Those sums are a gesture, not a replacement for a morning's takings.

Some very small firms run on a residential broadband package. They are inside the Ofcom scheme, but the amounts are the same small ones, and it is worth checking whether the package terms allow business use.

The conclusion: an SLA makes the supplier accountable for how fast it responds. It does not make you whole. Ask your insurer whether your business interruption cover includes loss of telecoms, and assume that keeping yourself online is your job.

Repair times: care levels and what "business grade" buys

Most UK business broadband runs over Openreach's network, and Openreach sells providers different "service maintenance levels". At level 1, the target is to fix a fault by 23:59 two working days after it is reported, counting Monday to Friday. At level 2, the target is 23:59 on the next working day, counting Monday to Saturday. Openreach says it offers the same levels for home and business products, and that your provider can tell you which one applies to your line 3.

Faster levels have existed for years. An Ofcom review of services for small businesses noted that the highest level Openreach offered for wholesale broadband and landline services carried a six-hour repair target, and that this option was not widely offered by business providers 4. If a quick fix matters to you, ask exactly which level is in the price and what an upgrade costs.

A leased line is a different product: a dedicated fibre connection that is not shared with other customers and gives the same speed in both directions. Provider guides describe typical leased-line SLAs of 99.95% availability or better with fix-time targets of four to six hours 6. Prices in 2026 start at around £200 a month for 100 Mbps and around £300 a month for 1 Gbps 5, and installation commonly takes 60 to 90 days 6.

So what does a "business broadband" package add over a residential one? Usually some combination of a fixed (static) IP address, priority support, an option for a faster care level, and a backup bundle. BT Business's Enhanced tier, for example, costs about £10 a month more than its Essential tier and adds 4G backup, technical support and a static IP address 1213.

One point is easy to miss. A faster repair shortens an outage. A backup removes most of its effect. For the same money, most small firms get more from a backup than from a faster fix. The firms that buy both are those for whom even the slower backup connection is a problem.

Backup options for businesses compared

OptionProtects againstIndicative cost, November 2026Switch-overWatch out for
Provider 4G add-onLine faults and outages on the provider's fixed networkBT Business: £8 a month ex VAT on Essential, included on Enhanced and Pro 7. Virgin Media Business "Constant Connect": £7 a month, or included in its Voom Fibre and phone-line bundles 10. Sky Business: included on higher tiers or as an add-on 9AutomaticWorks only with the provider's router; needs a mobile signal at your premises
Your own 4G/5G failoverThe same, with any providerDual-WAN routers: TP-Link ER605 about £49; DrayTek Vigor 2927 about £237 to £242 1415. DrayTek Vigor 2927Lac with built-in 4G: recommended retail price £529 plus VAT 16. Plus a data SIMAutomaticInbound connections on mobile; data allowance
Second fixed line on a different networkLine faults, and provider outages if the provider differsThe price of a second broadband packageAutomatic with a dual-WAN routerTwo lines that share a duct, pole or cabinet can fail together
SatelliteLocal cable and mast failuresStarlink residential plans from £40 a month 17; business plans priced separately and due to change on 1 December 2026 25Automatic with a dual-WAN routerNeeds a clear view of the sky; overkill where mobile signal is good
Leased line with a backup circuitMost things, with a contractual fix timeFrom about £200 a month for the leased line 5AutomaticCost; long installation times 6

Layering beats any single option. A fibre line plus mobile failover covers the common failures. Two fixed lines on different networks plus mobile covers nearly everything short of a power cut. Full fibre now reaches 82% of UK homes and gigabit-capable networks 89% 18, so many premises have a choice of physical network, for example an Openreach-based service alongside Virgin Media's cable network or an alternative full-fibre provider.

"Different network" means different cables. Two providers that both resell Openreach lines give you two bills and one point of failure. Ask each provider which network it uses to reach your building.

The mobile side of this (signal testing, SIM types, data planning) is covered in depth in 4G and 5G backup broadband.

Dual-WAN explained: failover vs load balancing

A WAN port is the socket on a router where an internet connection plugs in. A dual-WAN router has two, so it can manage two connections at once. The TP-Link ER605 and DrayTek Vigor 2927 are examples aimed at small offices; the DrayTek "L" models add a built-in 4G modem with two SIM slots 1516.

You can run the two connections in one of two ways.

Failover (active and standby). All traffic uses connection A. The router tests A continuously and moves everything to B when A stops working, then moves back. This is the simple choice and the right one when B is a mobile connection with a data allowance.

Load balancing (both active). The router spreads traffic across both lines, which adds capacity and still gives you failover. It suits two fixed lines of similar quality. The drawback is that different sessions leave through different IP addresses, and some services, online banking and phone systems among them, dislike a user whose address keeps changing. Good routers let you pin those services to one line. Do not load-balance on to a metered SIM.

Three practical points apply either way:

  1. The router decides when a line is "down". Good ones test whether the internet is reachable, not merely whether the cable is plugged in. The home setup guide explains detection settings and how to test them; the same principles apply in an office.
  2. The router is now your single point of failure. Keep a saved copy of its configuration, and consider a spare if a dead router would stop the business.
  3. Nothing works without power. Put the router, the fibre box (ONT), the main network switch and the phone system on a battery (UPS).

Keeping phones, card payments and cloud apps working on the backup

A backup that keeps web browsing alive but drops the phones has not done its job. Check each of these.

Internet phones (VoIP). Calls need little bandwidth, about 100 kbps of upload per simultaneous call by one industry guide's estimate 19, so a 4G connection carries them comfortably. Calls in progress will drop at the moment of failover, and handsets then reconnect to the phone service. Test it: make a call, pull the main line, and time how long the phones take to come back. If you buy a provider's backup, ask whether it supports that provider's phone service; BT's 4G backup is described as compatible with its digital phone line and static IP features 12.

Card payments. Terminals connect outwards to the payment processor, so they generally work over a backup provided they are on the part of your network that fails over. A terminal with its own mobile SIM is independent of your broadband altogether, which is a useful second route for a shop. Terminals that dial out over an analogue phone line are a separate problem, covered in the next section.

Cloud software and email. These connect outwards and carry on. Expect some services to ask users to sign in again because the office's public IP address has changed.

Anything that connects in to your office. Remote access to an on-site server, viewing CCTV from outside, a site-to-site VPN: all of these need to reach your router from the internet. Mobile networks commonly put customers behind a shared address (carrier-grade NAT, or CGNAT), which blocks that; EE's community support states that its mobile network does not provide a public address outside CGNAT 20. Your options are:

  • Use a provider backup that keeps your static IP address working during failover, and get that confirmed in writing.
  • Ask mobile providers about a business SIM with a fixed public IP address. Specialist providers sell them, but availability and pricing vary by supplier 24.
  • Use a VPN or tunnelling service that connects outwards from your office, so no inbound route is needed.
  • Move the service to the cloud, so that nothing needs to reach in.

IP allow-lists. If a bank, supplier or software platform only accepts connections from your office IP address, it will refuse you on the backup. Register the backup's address in advance if it is fixed, or route that traffic through a VPN with a fixed exit address.

Data discipline. Set the router to block guest Wi-Fi, software updates and cloud backups while on a metered backup.

The landline switch-off checklist for business premises

The analogue phone network (PSTN) is due to be retired by 31 January 2027, along with the Openreach products that run over it. In February 2026 Openreach said more than half a million business lines still needed to upgrade 11. The change affects more than telephones. BT lists alarms, point-of-sale machines, door entry systems, CCTV and fax machines among the devices that may be affected, and has tested lift auto-diallers, telemetry devices and security alarms in its labs 21.

Work through this list:

  1. Walk the premises and note everything plugged into a phone socket, including sockets in plant rooms, lift motor rooms and behind the till.
  2. Call each supplier: alarm company, lift maintainer, payment provider, door-entry installer. Ask whether the device works on a digital line and what they recommend.
  3. Ask what the replacement uses to communicate. If it uses your broadband, it now depends on your connection and your power. If it uses its own mobile signalling, it is independent of both.
  4. Check for ISDN lines on older phone systems; these are withdrawn at the same time 11.
  5. Move your numbers. Ask your new phone provider to port the numbers you advertise.
  6. Test in a simulated power cut. Digital phone lines need mains power to work 22.

After the switch, your phone service is an application running on your broadband. An outage that used to leave the phones working will now take them down too. That is the strongest single argument for sorting out a backup this winter. Openreach has described temporary measures for lines that are not migrated by the deadline, but they are a stopgap with limits 23.

Right-sizing: sole trader, small office, larger site

Sole trader or home office (one or two people). A phone hotspot may be all you need. If you take client calls all day, add automatic 4G failover with a provider add-on or your own router. The household-level comparison is in ISP backup vs DIY vs satellite.

Small office, 3 to 20 staff, mostly cloud-based. Business full fibre, plus automatic 4G or 5G failover through a provider add-on or a dual-WAN router, plus a battery for the network equipment. Test it once a quarter. This is the best-value tier and where most firms should stop.

20 to 50 staff, or anything revenue-critical. Two fixed lines on different physical networks through a dual-WAN router, with mobile as a third path. Consider a leased line as the primary if you need guaranteed upload speed or a contractual fix time. Write down who does what when the main line fails, and make sure the static IP question is answered.

Shops, cafés and clinics. Give the card terminal its own route (a terminal with a built-in SIM), keep the booking system and phones on the failover network, and protect the router and fibre box with a battery.

When it is not worth it. If staff can work offline for a day, or go home and work there, and you take no payments or calls over the connection, a paid backup may never repay its cost. Keep a hotspot plan and move on.

Questions to ask a provider before you sign

  1. Which physical network delivers this service to my premises?
  2. Which repair level is included, and what does the next level cost?
  3. Is there an SLA? What exactly triggers a credit, and how much is it?
  4. If backup is included, which mobile network does it use, and is the data unlimited?
  5. Does my static IP address keep working during failover?
  6. Do your phone service and my card terminals work over the backup?
  7. Can I use my own router, and does the backup still work if I do?
  8. How do I test the failover, and will a test count against any allowance?
  9. What is the contract length, and what are the annual price rises?
  10. What happens to the backup if I change package or leave?

FAQ

Does Ofcom's automatic compensation apply to business broadband?

No. The scheme is described as covering residential fixed broadband and landline products 1. Businesses on business contracts rely on the SLA and service credits in their contract.

What is the cheapest way to add failover to a business connection?

A provider add-on if your provider sells one: BT Business charges £8 a month excluding VAT on its Essential tier 7 and Virgin Media Business £7 a month 10. Otherwise, a dual-WAN router from about £49 14 with a 4G modem or router and a data SIM.

Do I need a leased line?

Only if you need what it uniquely provides: a dedicated connection, equal upload and download speeds, and a contractual fix time, typically four to six hours 6. At £200 a month and up 5, it is hard to justify for outage protection alone when mobile failover costs a fraction of that.

Will my internet phones work on a 4G backup?

Usually, yes. Calls need little bandwidth 19. Calls in progress will drop when the connection switches, and handsets then reconnect. Test it with your own phone system before you rely on it.

Can I keep my static IP address on the backup?

Not automatically. A mobile backup normally gives you a different, shared address 20. Some provider backups are designed to keep a static IP working; BT's is described as compatible with its static IP feature 12. Get it confirmed for your package.

Is load balancing better than failover?

It is better when you have two fixed lines of similar quality and want to use both. For a fixed line with a mobile standby, plain failover is simpler, cheaper on data and less likely to upset services that expect a stable address.

What happens to my alarm or card machine when the analogue network closes?

Devices that dial out over an analogue line may stop working or behave unpredictably on a digital line 21. Contact the supplier of each device now and ask for a version that uses broadband or mobile signalling.

Sources

Checked 13 November 2026.

  1. Ofcom, "Automatic compensation: what you need to know" (rates from 1 April 2026): ofcom.org.uk
  2. Beaming, "£3.7bn: the cost of internet failures to UK businesses", March 2024: beaming.co.uk
  3. Openreach, "Our performance FAQs" (service maintenance levels): openreach.com
  4. Ofcom, "Comparing service quality" (section on small and medium-sized businesses): ofcom.org.uk
  5. Babble, "How Much Does a Leased Line Cost in the UK in 2026?", 9 January 2026: babble.cloud
  6. CloudSwitched, "Leased Line Cost in the UK: 2026 Pricing Guide": cloudswitched.com
  7. BT Business, "Business broadband deals" (package comparison): business.bt.com
  8. BT Business, broadband terms ("Hybrid Backup and Always Connected Guarantee"): business.bt.com
  9. Sky Business, "Ultrafast broadband" (4G back-up and Stay Connected Guarantee): business.sky.com
  10. Virgin Media Business, "Voom 4G Back-up for Business Broadband" (Constant Connect): virginmediabusiness.co.uk
  11. Openreach, "Time for a 'big switch-up' as PSTN switch-off looms", 5 February 2026: openreach.com
  12. Ken's Tech Tips, "BT Business Broadband" (Enhanced tier features): kenstechtips.com
  13. Choose.co.uk, "BT Business broadband review": choose.co.uk
  14. Mighty Gadget, "Best dual WAN routers" (TP-Link ER605 and DrayTek Vigor 2927 listings): mightygadget.co.uk
  15. Scan, "DrayTek Vigor 2927 wired router" (price viewed November 2026): scan.co.uk
  16. ProVu, "DrayTek Vigor 2927 Router Series" (specifications and recommended retail prices): provu.co.uk
  17. Broadband.co.uk, "Starlink broadband deals" (prices checked 2 November 2026): broadband.co.uk
  18. Ofcom, "Connected Nations update: Spring 2026", 13 May 2026: ofcom.org.uk
  19. Selectra, "Small business broadband" guide, 2026: selectra.co.uk
  20. EE Community, thread on public IP addresses and CGNAT on EE mobile broadband: community.ee.co.uk
  21. BT, "What does the PSTN switch off mean for your devices?": bt.com
  22. Ofcom, "Future of landline calls": ofcom.org.uk
  23. ISPreview, "Openreach confirm post-January 2027 measures for UK analogue phone switch-off", 24 September 2026: ispreview.co.uk
  24. Andrews & Arnold, "Fixed IP, 4G and 5G data SIM cards" (example of a SIM with a fixed public IPv4 address): aa.net.uk
  25. ISPreview, "Starlink Cut 100Mbps UK Satellite Broadband Plan to £32 as Other Prices Rise" (business plan changes from 1 December 2026), 30 October 2026: ispreview.co.uk

General information for UK households and small businesses, not legal, financial or technical advice. Facts checked on 13 November 2026; prices, coverage and rules change, so confirm the details with a provider before you buy.

Next guideHow to Set Up Automatic Broadband Failover at Home, Step by Step