Will my digital landline work in a power cut?

If your landline has moved to digital — Digital Voice, Digital Phone, or whatever your provider calls it — then it runs over your broadband connection. Your router needs mains power. So when the electricity goes off, the phone goes off with it, immediately and completely.

This is the single change that catches people out most in the landline switch-off, and it is worth understanding properly rather than being reassured about, because the fix has a part that most explanations leave out.

Why the old line kept working and the new one does not

The analogue phone network powered your handset down the copper wire, from the local telephone exchange. That is why a plain corded phone worked in a power cut: it never needed anything from your house except the socket in the wall.

A digital landline is a call carried over your broadband. The equipment doing the work now sits in your hallway rather than at the exchange, and it runs on your electricity. Ofcom puts it plainly: calls made over broadband will not function in a power cut, because the broadband equipment at the premises requires mains power, so calls are only possible if additional protection measures are put in place.

What the rules actually say

This is where a lot of what you will read online is subtly wrong, so here is the precise position.

The binding rule is not about batteries or hours. It is General Condition A3.2(b), which requires that regulated providers “must take all necessary measures to ensure … uninterrupted access to Emergency Organisations as part of any Publicly Available Telephone Services offered”. “Emergency Organisations” means the police, fire, ambulance and coastguard services. That duty is real and enforceable, and it applies whatever technology your calls run over.

The one hour is guidance, not law. In October 2018 Ofcom published guidance on how providers can meet that duty, built around four Principles. The first is that providers should have at least one solution available that enables access to emergency organisations for a minimum of one hour in the event of a power outage at the premises. Ofcom is explicit that the guidance “will not have binding legal effect and each case will be considered on its own merits”, and that it is not the definitive guide to compliance.

That distinction is not pedantry — it changes how you ask. You are not citing a statutory entitlement to a battery. You are asking your provider how they meet a binding duty to keep you able to call 999, and pointing at the solution Ofcom expects them to have available.

Free is for people who depend on the line, not for everyone. Ofcom’s second Principle is that the solution should be suitable for the customer’s needs and should be offered free of charge “to those who are at risk as they are dependent on their landline”. Ofcom describes those customers as people without access to a mobile or without reliable indoor mobile coverage, people who are housebound, and people with a greater need to call emergency organisations because of their circumstances. If that is your household, say so in those words.

Ofcom does not require a battery specifically. The 2018 guidance asks for “at least one solution” and is deliberately technology-neutral. A battery back-up unit is the usual answer, and providers mostly supply one — but the battery-specific rule people half-remember (“a battery back-up should always be provided”, “the minimum duration should be 1 hour”) is from Ofcom’s older 2011 guidance for fibre-to-the-premises services, which the 2018 guidance replaced.

Providers are supposed to come and find you. The third and fourth Principles say providers should take steps to identify at-risk customers, communicate the risk and the eligibility criteria clearly enough that people can request the solution, and have a process for customers who move house or whose circumstances change. In practice this is patchy, which is why asking beats waiting.

The trap: a battery does not save a cordless phone

This is the part that undoes an otherwise sensible plan, and almost nothing written for consumers says it clearly.

The back-up unit powers the router. A cordless phone does not run off the router — its base station plugs into the mains on its own, and cordless handsets do not generally carry a back-up battery. So in a power cut the base station is simply dead, and it makes no difference at all that the router beside it is still humming away on battery.

This is not an edge case. Ofcom’s own research found that 68% of people who have a landline at home have a cordless phone only, and that half of the people living in a home whose only phone is a landline use a cordless handset rather than a corded one. Ofcom’s assessment is blunt: cordless phones are very unlikely to work in a power cut, because the unit that plugs into the phone socket also needs mains power and does not tend to have a battery.

So the plan is two things, not one. A back-up for the router, and a basic corded phone kept somewhere you can find it in the dark. A corded handset costs a few pounds. It is the cheapest part of the whole arrangement and the one most often missing.

How to ask, and what to ask for

Work through the ordered steps below — they are written so you can follow them on someone else’s behalf, which is how most of these calls actually happen.

1. Work out whether anyone here depends on the landline. Is there a working mobile in the house? Does it get a reliable signal indoors? Is anyone housebound, or more likely than most to need to call 999? If the landline is the fallback, this is the household Ofcom’s free-provision expectation is written for.
2. Check the indoor mobile signal properly rather than assuming. Stand where the phone normally lives. One bar in the kitchen and nothing in the bedroom is not a mobile fallback for someone who has fallen over. Our fix mobile signal at home tool walks through what can be improved and what cannot.
3. Ring your provider and ask for the power-cut solution by name. Say your landline is now delivered over broadband, that someone in the household is dependent on it, and that you are asking for the power-cut protection solution Ofcom expects providers to have available. Ask for it free on the grounds of dependence, and ask them to note the reason on the account.
4. Ask exactly what it powers, and for how long. Router only? How many minutes? Does it cover the phone you actually use? One hour is Ofcom’s stated minimum expectation, not a promise your provider has made — make them state their own number.
5. Buy a corded phone and keep it with the kit. See above. This is the step people skip.
6. Test it once, deliberately. When it is installed, switch the power off at the consumer unit, plug in the corded phone, and make one call to a mobile. Proving the chain works on a quiet afternoon beats discovering a missing cable during a real power cut.
7. Tell them separately about any alarm or telecare pendant. Power-cut protection for the phone line and telecare equipment are handled as separate things by providers. If anyone uses a fall detector, medical alarm, monitored alarm or care-line pendant, raise it with your phone provider and the organisation that supplies the alarm — see telecare alarms and the digital switchover.

If your provider says no

Ask them to record the request and the refusal, and to explain how they meet General Condition A3.2(b) for a customer in your circumstances. Get it in writing — an email or the transcript of a chat is fine.

If that does not resolve it, use their formal complaints process, and then take it to their alternative dispute resolution scheme. Every provider must belong to one of the two approved schemes, Communications Ombudsman or CISAS, and going to them is free. You can escalate once you have a deadlock letter, or six weeks after the date you first complained. Our complaint letter generator will put the request into a form that is hard to brush off.

A last word on honesty

An hour of back-up is an hour. It is enough to call 999 and to call a relative. It is not enough to keep a household connected through a long winter outage, and nobody should plan on the basis that it is.

If someone in the house genuinely cannot be out of contact — because of a health condition, because they are housebound, or because there is no usable mobile signal — treat the battery as the minimum rather than the answer, and have a second plan: a charged mobile kept in a known place, a neighbour who will check in, and the telecare provider’s own advice about what their equipment does when both the power and the broadband are gone.

→ Use the fix mobile signal at home tool