Test each circuit breaker safely, note what it controls, then label your consumer unit clearly for future reference.
CU-01Gather your tools and a helperYou need a torch, a notepad and pen, and sticky labels or a printed label sheet. Ask someone to help — one person flips switches at the consumer unit, the other checks lights and sockets around the house. Do this in daylight if you can, so a light going off isn't confusing.
CU-02Find your consumer unit and check the RCDThe consumer unit is usually in the hall cupboard, garage, or under the stairs. You only need to use the switches — don't remove the front cover. Press the small test button marked 'T' on each RCD switch; it should trip off immediately. If a switch doesn't trip when tested, stop and get a qualified electrician to check it before you rely on it.
CU-03Warn the household and check appliancesTell everyone in the house you're about to switch circuits off and on. Save any work on computers first. Wait until the washing machine, dishwasher or boiler aren't mid-cycle, since cutting power partway through a cycle can cause an error or a rewash.
CU-04Turn off every small breaker, leaving the main switch onNote down anything already labelled, even if it looks wrong. Flip all the small circuit breakers to off, but leave the large double-pole main switch on. This gives you a blank slate to test each circuit one at a time.
CU-05Switch on one breaker and test what it powersFlip the first small breaker on. Walk round the house, or send your helper, checking which lights come on and which sockets have power. Plug a lamp or phone charger into a few sockets on each floor to test them, and check the boiler display, doorbell and smoke alarms too, as these often sit on their own circuit.
1 each · Plug-in lamp or phone charger (for testing sockets)
CU-06Write down what each breaker controlsNote exactly what came on for that breaker, using clear wording like 'kitchen sockets' or 'upstairs lights'. Turn that breaker off again before testing the next one, so you don't mix up the results between two circuits.
CU-07Repeat for every remaining breakerWork through each switch in turn until they've all been tested and noted. Some circuits, like the boiler, immersion heater or smoke alarms, don't have an obvious sign of power — listen for a click or check for a small indicator light instead.
CU-08Turn everything back on and double-checkSwitch every breaker back to on. Walk round the house again and confirm all lights, sockets, the boiler, fridge and freezer have power. This confirms nothing has been left off by mistake before you finish up.
CU-09Write and fix clear labelsUsing your notes, write or print a short, specific label for each breaker, such as 'Kitchen sockets' or 'Landing and bathroom lights'. Stick each label directly above or below its switch, or fix a labelled card inside the consumer unit door if there's no room on the switches themselves.
CU-10Tidy up and keep a backup recordTake a photo of the finished, labelled consumer unit on your phone. Keep a written copy of the list somewhere handy, like a kitchen drawer, in case a label ever falls off. This saves time next time you need to isolate a specific circuit for another job.
Some links may earn us a small commission at no extra cost to you.