A power-cut communications plan (UK)

If the power goes off, assume your broadband stops with it and your mobile signal may not last. This guide sets out what the UK rules and reports say about each, then a short plan for the part a LoRa mesh can help with: short text messages between neighbours.

What happens in a power cut

As of 2026-10-29, from the sources linked on this page:

Because the old network is being retired, do not assume "the landline still works in a power cut". After the switch it works only if your own router or adapter and handset are on a battery and the network path to the street cabinet and exchange stays powered.

What the rules guarantee

• Landline users with no mobile. Ofcom says that if you depend on your landline and have no working mobile or reliable signal, your provider must offer you, for free, a back-up solution such as a battery back-up unit. Ofcom's page says it must last at least one hour, though some providers' back-ups last up to seven hours. Ofcom's 2018 guidance on General Condition A3.2(b) sets one hour as a minimum and says some customers may need more.
• 999 on another network. Ofcom says calling 999 from a mobile will automatically connect through another network if yours has no signal and another is available. It needs at least one network.
• No fixed number of hours for masts. Bratby Law's reading of Ofcom's 16 June 2026 resilience guidance is that it does not set a fixed number of hours of battery; it is risk-based. We read this through Bratby Law and Ofcom's landing page, not the guidance PDF itself.
• Street cabinets. Bratby Law summarises the same Ofcom guidance as treating 3 to 4 hours of power backup as good practice for new active fixed access cabinets, with more where outages are longer or more frequent. Again, we did not open Ofcom's PDF.

How long do mobile masts last?

There is no single answer, and the figures below are second-hand. ISPreview, reporting Ofcom's February 2025 mobile power resilience technical report (we did not open the report itself), says:

• about 20% of UK mast sites have backup of at least 1 hour, and only about 5% have at least 6 hours;
• for outages of up to about 1 hour, around two thirds of the population could make emergency calls;
• the backup covers emergency calls and not necessarily data or calls to any number;
• citing Ofgem data, about 90% of power outages last between 3 minutes and 3 hours.

For a long event, the EC-RRG report on Storm Arwen (November 2021) said thousands of mobile cell sites were disrupted, all four mobile operators were affected, and battery resilience was depleted after a number of hours. It describes that battery as intended to keep sites running through brief intermittent outages. See storm and flood readiness for more.

Before it happens

• Check the Priority Services Register. The government's Be Ready campaign (launched 22 October 2026) asks households to sign up. The E3C Storm Arwen review noted the register did not capture people who only became vulnerable because of how long they were without services, so neighbours checking on each other still matters.
• Be Ready's three-day idea. The campaign advice is to be ready for three days of disruption, and to keep non-perishable food and bottled water. We could not read the campaign's full checklist, so we do not say what else it lists.
• Know 105. 105 is the free national number to report or get information about a power cut; it connects you to your local electricity network operator, whoever your supplier is. It launched on 6 September 2016 for England, Scotland and Wales (SSE press release). It is for faults, not an emergency number, and you need a working phone. Northern Ireland uses a different arrangement through NIE Networks, which publishes a power cut, faults and outage information page; we have not confirmed the number, so we do not print it.
• Charge phones and power banks when a storm is forecast. See Power, including why some power banks switch off a low-draw node.
• If you rely on a digital landline, ask your provider about the battery back-up Ofcom describes, and check how long it lasts.

Where a LoRa mesh fits

A mesh moves short text between people you have already equipped and who are within radio reach. That is all. It does not call 999, reach the internet, restore broadband or replace the food, water and register steps above. A single node reaches nobody, so it only helps if neighbours also have nodes. Use find a local mesh to see whether anyone nearby does, and what you can actually do for the limits.

In the UK the radio runs on 868 MHz (Meshtastic region EU_868). The usual slot, 869.40 to 869.65 MHz, allows 500 mW e.r.p. at a 10% duty cycle under Ofcom IR 2030 v1.16 (published 7 April 2026). Meshtastic documents a 10% duty cycle for EU_868, calculated every minute over a rolling hour. No licence is needed within those limits. Details are on UK radio rules at a glance. We give no range or battery-life figures because we have no sourced ones; see resilience in practice for what has and has not been documented elsewhere.

A minimal street plan

1. Agree who on the street has a node, and write each person's node name and phone number on paper.
2. Set the same region (EU_868) and preset on every node, and use a private channel for the group. The default channel's key is public; see privacy and encryption.
3. Agree a check-in time, for example once in the evening, so everyone knows when to look. Keep messages short, because airtime is limited by the duty cycle.
4. Keep one node charged on a power bank or small battery. Test it before you need it, and see solar node tool if you want to size a panel.
5. Put the first-choice routes on the same sheet: 999 or 112 for emergencies, 105 for power faults, and who checks on any neighbour who is vulnerable.

Limits

• Mesh needs other people with nodes close by. If nobody does, it does nothing.
• It does not fix a lack of mobile signal for 999 calls.
• It is not a broadband alternative. See the ISP as a single point of failure and community broadband alternatives.
• BT's 31 January 2027 date applies to BT and Openreach customers. This page will go out of date after that; check the updated date.

FAQ

Will my landline work in a power cut?

Ofcom says digital landlines need mains electricity and will not work in a power cut unless there is battery back-up. BT plans to retire its old landline network by 31 January 2027, so expect to be on a digital line soon if you are not already.

Will my mobile work in a power cut?

Possibly, for a while. ISPreview, quoting Ofcom's 2025 report, says about 20% of UK mast sites have at least 1 hour of backup and about 5% at least 6 hours. Coverage depends on the masts near you.

What number do I ring to report a power cut?

105 in England, Scotland and Wales. It is free and connects you to your local network operator. For an emergency, such as a person in danger, call 999 or 112.

Can Meshtastic or MeshCore call 999 in a power cut?

No. Neither can contact the emergency services. A message only reaches people with nodes in radio reach, and one of them would have to use a phone to call 999 on your behalf.