Will my landline work in a power cut?

Not if it's digital, unless it has battery backup. Ofcom says digital landlines need mains electricity. Phones that plug into your router stop when the power goes.

Does BT Digital Voice work in a power cut?

No, unless you have a battery backup unit. Providers must offer at least one hour of emergency access, free, to customers who depend on their landline.

When does the analogue phone network switch off?

The PSTN closes on 31 January 2027. Lines not moved by then go onto a temporary, limited emergency-only service run by Openreach.

How long does mobile signal last in a power cut?

It varies by mast. Ofcom found about 20% of mast sites had an hour of battery backup and 5% had six hours, so coverage falls away over the first few hours of a long cut.

Will Your Landline Work in a Power Cut? Digital Voice Explained (UK)

The switch to digital

The old analogue phone network, known as the PSTN, closes on 31 January 2027 (Ofcom). Calls now go over broadband instead, a service BT calls Digital Voice. About 15 million lines have already moved, and about 1.2 million were still to go in September 2026 (ISPreview). From 1 February 2027 Openreach will move any lines left on the old network to a temporary, limited emergency-only service, putting telecare lines first (Openreach).

What happens in a power cut

The old copper line carried its own power from the telephone exchange, so a corded phone kept working when the lights went out. A digital line doesn't. In Ofcom's words: "Digital landlines need mains electricity and will not work in a power cut unless there is a battery back-up" (Ofcom). Your router and the phone's base station both need power.

The backup you're entitled to

Phone companies must offer a way to reach the emergency services for at least one hour in a power cut, free of charge, to customers who depend on their landline: people with no mobile, no reliable mobile signal at home, or a disability that means they rely on the landline. Providers are expected to find those customers. Ofcom set the rule in 2018 and restated it in June 2026, and some providers' battery units last up to seven hours (Ofcom guidance, Ofcom). If that's you or a parent, ask your provider for the battery backup by name.

Care alarms

Ofcom warns that telecare and personal alarms "might not work properly on a digital landline", and asks users to tell both their phone provider and their alarm supplier before switching (Ofcom). Under the industry charter agreed with the Government in December 2023, providers shouldn't move a telecare user until they have a working solution, and aim to provide backup for longer than Ofcom's hour (GOV.UK).

Will your mobile still work?

For a while. Mobile masts need power too. Ofcom found in 2025 that only about 20% of mast sites had an hour of battery backup, and 5% had six hours. After an hour-long power cut about two-thirds of people could still call 999, helped by phones roaming onto any network for emergency calls, but after six hours far fewer could (Ofcom). In Storm Arwen in 2021, more than 74,000 customers were without power for over 48 hours and thousands of mobile sites were disrupted across all four networks, the same Ofcom report notes. In the Iberian blackout of April 2025, the share of Spanish users with a steady mobile connection fell from over 90% to about 40% by the afternoon as mast batteries ran out (TelecomTV).

Emergency Alerts reach 4G and 5G phones that are switched on and in range of a working mast, with no data or wifi needed (GOV.UK). If the masts near you lose power, assume alerts won't arrive, and listen to the radio.

What to do now

Find out what you have. If your phone plugs into the router, it's digital and it will stop in a power cut.
Ask for battery backup if anyone in your home depends on the landline. It's free for them.
Keep a mobile charged, with a power bank per phone. 112 works the same as 999 (GOV.UK).
Know the numbers. Report a power cut on 105, free from most phones in England, Scotland and Wales (Power Cut 105).
Keep a battery or wind-up radio and a torch, and don't use your phone as a torch, the Government's Be Ready advice says.
Agree a meeting point with your family in case the phones go down altogether.

Every T-⁠MINUS kit includes a 20,000 mAh power bank and a wind-up radio. From T+7 there are licence-free walkie-talkies and a 1 kWh power station that can keep a router running, and T+30 adds a two-way satellite messenger with SOS that needs no mobile signal at all.

Will your landline work in a power cut?