Power cuts and 999 calls

What stops working in a power cut

With full fibre, the fibre box on your wall and your router both run on mains electricity. If the power goes off, your broadband stops until it comes back. So does anything that works over your broadband, including:

• phone calls over the internet (often called VoIP or a digital landline)
• telecare and personal alarms that connect through your router
• alarm systems, lift lines and payment terminals that use your connection

Old analogue phone lines carried their own power from the exchange, which is why a corded phone could keep working in a power cut. The UK is retiring that network, and it is due to be switched off by the end of January 2027, so this now affects most homes and businesses whoever their provider is. Our guide to the UK landline switch off explains more.

Making 999 calls in a power cut

For most people, a mobile phone is the simplest way to call 999 during a power cut. Keep it charged, and consider a charged power bank. You can call 999 or 112 from a mobile even without credit.

A battery backup unit (sometimes called a UPS) can keep your router and fibre box running for a while during a power cut. How long depends on the unit and your equipment.

If you rely on a landline

Please tell us, and your phone provider, if anyone at your address:

• has a telecare or personal alarm, or other equipment that uses the phone line
• has no mobile phone, or no reliable mobile signal at home
• would struggle to use a mobile phone in an emergency

Ofcom requires providers of phone services over broadband to offer customers who are at risk at least one solution, free of charge, that lets them call 999 for at least one hour during a power cut, such as a battery backup. If your phone service is from another provider, please ask them about this.

When you order from us online, you can tick the box on the details step to let us know. You do not need to tell us why. We will talk to you before your installation so nothing is left to chance.

Telecare and personal alarms

Before you switch, tell your alarm provider that your connection is changing to full fibre. Some older alarms do not work reliably over a digital connection. Your alarm provider can check, and many can test the alarm after installation. Please also tell us, so our engineer knows.

For businesses

If your premises has alarms, lift lines, door entry or payment terminals that use a phone line or your broadband, ask each supplier how it behaves in a power cut and whether it has its own backup.