A power cut in brief

Report it on 105 in England, Scotland and Wales: the free number puts you through to the company that runs the power lines in your area (Ofgem). In Northern Ireland the number is 03457 643643 (Be Ready).
Keep doors shut. A closed fridge keeps food safe for up to about four hours; a full freezer for about 48 hours, a half-full one for about 24 (Food Standards Scotland).
Stay safe. Never bring a barbecue, camping stove or generator indoors: carbon monoxide can kill (Dorset & Wiltshire Fire and Rescue).
You may be paid. Homes cut off for more than 12 hours in normal weather get £100 from the network operator, usually without claiming (Ofgem).
Be ready for three days. The government's Be Ready checklist asks every home to keep water, food, light, a battery or wind-up radio, a power bank, cash and copies of documents (gov.uk).

What the app does

It starts with one question: what do you need right now?

The power has just gone off: eight steps in the right order, from the fuse box to checking on neighbours, with the time noted for the other tools.
Build our three-day kit: the official list with water, meals and warm layers worked out for the adults, children, babies and pets in your home.
Am I owed a payment? Ofgem's guaranteed payments for normal faults and storms, from the hours you were without power.
Is the food still safe? A fridge and freezer clock that keeps counting from the moment the power went.