On a full fibre connection, a power cut at your home will usually stop your broadband, and with it any home phone that runs over the connection. This is because the equipment that makes it work, your router and the connection box, all need mains electricity. The older analogue landline drew a small amount of power from the exchange and often kept working in a power cut, but a modern digital phone service depends on your powered equipment, so it stops when the power does.
This matters most for the ability to make calls in an emergency. The good news is that it is straightforward to plan around once you understand it, and there are specific resilience options for people who need them. This guide explains why a power cut takes down your connection, what it means for your phone, the backup options available, and how to make sure you can still get help when the power is out.
Arrangements vary between providers and connection types, so treat this as general guidance and confirm the specifics, including any resilience support, with your provider.
Why does a power cut stop full fibre broadband?
Your connection relies on a small chain of powered equipment in your home. There is typically a connection box where the fibre terminates, and a router that creates your Wi-Fi and manages the service, and both run on mains power. The moment the electricity is cut, that equipment shuts down and the connection drops, even though the wider fibre network may be perfectly healthy.
The contrast with the old analogue landline surprises many people. A traditional phone received power down the line itself, so a basic corded handset could still make calls during a power cut. A digital phone carries calls as data over your powered equipment, so when that equipment loses power, the phone goes quiet along with the broadband.
What does this mean for your home phone?
As the analogue network is retired and homes move to a digital phone service, often delivered over your broadband, the phone plugs into your router rather than a wall socket. It works just like before for everyday calls, but it shares the broadband's dependence on power. If the electricity fails, you cannot rely on the home phone to call for help unless you have arranged a backup.
Because of this, there is a recognised need to protect people who depend on their landline, particularly those without a mobile or who rely on a phone for care or safety. Providers are expected to offer a resilience solution to vulnerable customers so they can still contact emergency services during a power cut, which is worth asking about if it applies to you or someone in your household.
What backup options keep you connected?
The simplest and most dependable backup is a charged mobile phone, because mobile networks run on their own power and are independent of the electricity at your home. Keeping a power bank charged means you can also top the phone up during a longer outage. For many households, a mobile is all the backup they need.
For internet specifically, a mobile hotspot or a separate mobile broadband device can provide a temporary connection, again assuming it has charge and there is mobile coverage. If you want your router and digital phone to keep working for a while, a battery backup unit can power them for a limited time. Anyone who depends on their phone for medical or care reasons should treat a suitable backup as essential and ask their provider what resilience support is available.
| Backup option | What it keeps running | Good to know |
|---|---|---|
| Charged mobile phone | Calls and basic data | Most reliable; independent of home power |
| Power bank | Recharges devices | Extends mobile use in longer outages |
| Mobile hotspot or mobile broadband | Temporary internet | Needs charge and mobile coverage |
| Battery backup for the router | Broadband and digital phone | Runs for a limited time only |
The table compares the common choices. Most households pair a charged mobile with a power bank, and add a router battery only if keeping the home phone or broadband alive really matters to them.
How can you prepare before a power cut?
Preparation is mostly about readiness. Keep a mobile phone charged and a power bank topped up, and make sure someone in the household knows how to use mobile data if the broadband is down. Store important numbers somewhere you can reach without the internet, and know roughly how long your chosen backups last.
If you or someone you live with relies on the phone for care, contact your provider to ask about resilience support for vulnerable customers, and check how any telecare or alarm device behaves when both power and broadband are out. A little planning now means a power cut is an inconvenience rather than an emergency.
Frequently asked questions
Why did my old phone work in a power cut but the new one doesn't?
The old analogue line received power from the exchange, so a corded phone could work in an outage. A digital phone carries calls over your router, which needs mains power, so it stops when the electricity does.
Will a battery backup keep my broadband on?
A battery backup or uninterruptible power supply can keep your router and connection box running for a limited time, which keeps your broadband and digital phone alive for a while. It is a short-term measure rather than an indefinite one.
Is my mobile affected by a power cut at home?
Generally no. Mobile networks have their own power and are independent of your home electricity, so a charged mobile usually keeps working during a local power cut.
What if I rely on my landline for care or safety?
Ask your provider about resilience support for vulnerable customers, which is intended to let you contact emergency services during a power cut. Also check how any telecare or alarm device behaves when power and broadband are out.
Bringing it together
On full fibre, a power cut stops your broadband and any digital phone running over it, because the equipment needs mains power. The most dependable backup is a charged mobile, ideally with a power bank, and a battery unit can keep your router going for a while. If anyone in your home relies on the phone for care, ask your provider about resilience support, and prepare in advance so a power cut never leaves you unable to call for help.