No Power in Half the House or One Room?

When the lights go out in one room, half the house or the whole property, the first question is whether the problem is inside your home or on the network supplying it. The answer decides who you need to call. This guide walks through the checks in order. None of them involve removing covers or touching anything inside the consumer unit.

Step one: is it a power cut?

Look outside. Are the street lights on? Do your neighbours have lights on? If the whole street is dark, it's almost certainly a power cut. In Great Britain you can call 105, free, to report it or find out what's happening. The network operator for your area will have information on the cause and expected restoration time. There's nothing an electrician can do about a network fault, so 105 is the right call.

If you're the only house affected and nothing has tripped in your consumer unit, the problem may be with the supply to your property or the main fuse (the sealed fuse next to the meter). These belong to the network operator, not to you, so don't touch them. Call 105 and explain that only your property is off.

Half the house off: a tripped RCD

Many consumer units, particularly those fitted from the late 1990s to the 2010s, have two RCDs, each protecting a group of circuits. When one trips, every circuit it covers goes off at once, which is why it can look like half the house has lost power: perhaps the kitchen sockets and upstairs lights, while downstairs lights still work.

Open the consumer unit door and look for a switch in the off or middle position. To reset it, first unplug appliances on the affected circuits, then push the RCD fully down and back up. If it stays on, plug things back in one at a time to see which one trips it. Our guide on why an RCD keeps tripping covers this in more detail.

One room or one set of sockets: a single circuit

If only one room, or only the lights or only the sockets in one area, have gone off, a single circuit breaker (MCB) has probably tripped. It will be in the off position among the others. Switch it back on. If it trips again immediately, there's likely a fault on that circuit or an appliance on it, so leave it off.

If nothing on the board has tripped, check whether the dead sockets are fed from a fused spur (a switched plate with a small fuse) or whether a plug fuse has blown. A single dead socket is covered in our guide to a socket not working.

Older fuse boards

Some older homes still have rewireable fuses, ceramic carriers with fuse wire. A blown fuse won't look different from outside. Replacing fuse wire is not recommended unless you know exactly what you're doing; it's a sign the board is overdue for an upgrade and an electrician should look at it.

What not to do

• Don't remove the cover of the consumer unit or meter.
• Don't tamper with the main fuse or meter seals.
• Don't hold a trip switch on or keep resetting one that trips straight away.
• If there's a burning smell, smoke, heat or buzzing from the board, switch off at the main switch if safe and call for help.

When to call an electrician

Call an electrician if a device won't reset with everything unplugged, keeps tripping, or if part of the house is dead with nothing tripped and neighbours have power. These point to a fault in your wiring that needs testing to locate. Our fault finding service traces the cause and puts it right. Call 01235 430442, Monday to Friday, 7:30am to 5:30pm.