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Electrical power loss: what to do when the lights go out

By Rebecca Milligan

Find out how you can safely try to restore power if your electricity supply goes off, with advice from Which? Trusted trader Justin Bucknell, from Justin Bucknell Electrical Ltd.
electrical power loss means lights are out, so a girl reads next to oil-powered lamp during a power cut

So the electricity has cut out and you’re in the dark. The first thing to check is that it isn’t a power cut. The easiest way to do that is to look out of the window – do your neighbours have lights on? Obviously that’s a bit harder during the day, but interruptions in power can sometimes set off burglar alarms, so there may be some clues there too.

If it’s a power cut, you’ll simply have to wait it out. Get your torch or candles out, and use it as an excuse to finish off that ice cream in the freezer before it melts.

If you’re sure it’s not a power cut, take a look at your consumer unit (also called a fuse box). These are designed to let you restore power safely – although if you’re in any doubt, call an electrician to investigate. You can find a Which?-endorsed electrician in your area with Which? Trusted Traders.

Power cutting out means that one or more of your circuit breakers has tripped a fuse or RCD (residual current device) on the fuse box, which indicates a problem on one of the electrical circuits in your house. There will be multiple circuits in each house. Lights and plug sockets will be on different circuits, and there may be circuits for each room and each floor. Bathrooms and kitchens will most likely have their own circuits, too.

You can narrow down the source of the problem by identifying what does and doesn’t still have power. Is the power off in the whole house, or only in one room or one floor? It might be that your lights have gone off but the fridge is still working, or vice versa. If your consumer unit is well labelled, you may not need any further investigation to find the circuit where there’s a fault.

Restoring power

  • Find the RCD or fuse that has tripped to the ‘off’ or down position on your consumer unit.  
  • Before trying to push the RCD switch back up, push down each of the individual circuit-breaker switches (known as miniature circuit breakers, or MCBs). These are often a bank of black switches, next to the RCD that controls their circuits.  
  • Push the RCD switch back up to restore the power.
  • Next, push all the individual circuit breakers back up again one at a time. If you reach one that trips the RCD again, you’ll know that’s the circuit with a fault on it.
  • If there is a fault on a circuit, leave the switch for that circuit down. Push the rest of the circuit breakers up again and restore power to the areas of the house that are fault-free.
  • Call an electrician to investigate the area where there’s a problem.

Call-out fees are likely to be lower during normal office hours.  Check our article on how to find an emergency trader if you need immediate assistance.

Problems resetting the RCD switch

Sometimes an RCD switch appears to be stuck in the ‘off’ position or in the middle, and won’t easily return to ‘on’. Justin advises that certain makes of consumer unit will have RCDs that trip to a mid-position. In order to push these back up, you have to push them all the way down first, and then they will reset back to the ‘up’ or ‘on’ position.

These units can be confusing to consumers, because it can look as though there’s still a fault, but in fact it’s just a different re-set method.

Sometimes your RCD might not reset if there is a fault with how the circuit is earthed. In this instance it will trip off again whatever you do, and you will need an electrician to investigate further.

If you’re in any doubt, always call in a qualified professional electrician. Find an electrician in your area with Which? Trusted Traders.

Electrical installation terminology

Consumer unit

Otherwise known as a fuse box, this is where the electricity is controlled and distributed in your home. Often found under the stairs or in a cupboard, it’s made up of a main switch that turns all the electricity on and off, RCDs and circuit breakers (see below).

RCD – residual current device 

A life-saving safety feature found on sockets or in consumer units that cuts the flow of electricity in dangerous situations.

MCB – miniature circuit breaker

These are used instead of fuses in low-voltage electrical networks, and are more sensitive to fluctuations than fuse wire. They switch off the electrical network when they sense a fault in the circuit, preventing overloading and short-circuiting.

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