Power cut or a fault in your home? How to tell in London

When the lights go out, the first question is simple. Is the problem out in the street, or is it inside your home? The answer decides who you call. A network fault is fixed by the company that runs the cables in your area. A fault in your own wiring needs an electrician. Getting this right saves you time and money, and in London the check takes a few minutes.

Step one: look outside

Before you touch anything, look out of the window. Are the street lights on? Are your neighbours’ windows lit? In a block of flats, are the corridor lights working?

• Everyone is dark. This is very likely a power cut on the network. Your own electrics are probably fine.
• Only your home is dark. The fault is more likely to be inside your property, on your side of the meter.
• Half the street is dark. London streets are often fed by more than one cable. A fault on one of them can take out some houses and not others.

If you live in a terrace in Croydon, Wandsworth or Hackney, knocking next door is often the quickest test of all.

Step two: check the network operator

Most of London is served by UK Power Networks. Its website has a live power cut map and a list you can search by postcode. You can also call 105 or 0800 31 63 105. Both are free.

West London is different. According to the Mayor’s answer to the London Assembly, Hounslow, Ealing and Hillingdon are served by SSEN (Scottish and Southern Electricity Networks). You do not need to remember which is which. 105 routes you by postcode. We cover that split in more detail in power cuts in Ealing and Hounslow.

If the map shows a fault near you, there is nothing for you to fix. Report it if it is not listed, and wait for updates. UK Power Networks also offers text alerts and a free Priority Services Register for people who need extra help during a cut.

Step three: look at your consumer unit

If the street is lit and your home is not, go to your consumer unit. This is the box of switches, sometimes called the fuse box or fuse board. In houses it is often under the stairs or by the front door. In flats it may be in a hall cupboard, with the meter in a communal cupboard on the landing.

Look, do not open. You only need to see the switches on the front.

What you see	What it usually means	What to do
Main switch off	Someone turned it off, or it was knocked	Switch it back on once
An RCD switch down	A fault caused current to leak to earth	Reset once; if it trips again, unplug appliances and try again
One small switch (MCB) down	One circuit overloaded or faulty	Reset once; if it trips again, leave it off
All switches up, still no power	The supply is not reaching the board	Check the meter display, then call 105
Old fuse box with pull out fuses	A fuse wire may have blown	Do not repair fuse wire yourself; call an electrician

An RCD (residual current device) is the safety switch that cuts power when electricity leaks somewhere it should not, such as through a person. An MCB (miniature circuit breaker) protects one circuit from overload.

If something trips straight back off, do not keep forcing it. That switch is doing its job. Our guide on why electrics keep tripping explains how to find the cause.

Step four: check the meter

If every switch is up and you still have nothing, look at your electricity meter. A blank screen on a smart meter, or a prepayment meter that has run out of credit, can look like a power cut. On a prepayment meter, check the balance and any emergency credit first.

If the meter is blank and your neighbours have power, the fault may be in the cable or the main fuse that feeds your home. That main fuse, called the cutout, belongs to the network operator. It usually sits next to the meter in a sealed black or grey box. Never try to open it. Call 105 and tell them only your property is off.

When it is a fault in your home

If the problem is on your side of the meter, you need an electrician. Common causes in London homes include:

• a failed RCD or a loose connection in an older consumer unit
• water getting into a light fitting or an outside socket
• a faulty appliance that trips the board every time power is restored
• a broken connection on one circuit, often in older wiring

Our no power in the house service starts with these checks and works through each circuit until the fault is found. An electrician will test before switching anything back on, so the problem does not return as soon as they leave.

Why London homes get this mix of faults

London has a lot of old housing. Government figures from the VOA council tax stock of properties show that 29.1% of London homes were built before 1919, against 20.6% across England and Wales. Most of these have been rewired at least once, but many were rewired decades ago. Older consumer units and mixed wiring from different eras are common.

London also has a high share of flats, 57.2% of all homes. In a block, the supply to your flat may run through shared cables and a communal meter cupboard. That changes who you call. If your flat is off and the corridor lights are on, or the other way round, see our guide to no power in a flat.

Safety while you wait

• Use a torch, not candles, if you can. The London Fire Brigade attends thousands of electrical fires in the city and candles add another risk in the dark.
• Switch off heaters, irons and cookers so they do not come back on unattended.
• Keep fridge and freezer doors shut.
• If you smell burning or see scorch marks near a socket or the consumer unit, switch off at the main switch if it is safe to do so and do not switch back on.
• If someone has had an electric shock, do not touch them while they may still be in contact with the supply. Switch off at the mains if you can and call 999.

If you are in Croydon, our Croydon area page covers the housing there and the faults it tends to produce. Wherever you are in London, start with the window, then 105, then the consumer unit. That order tells you who can actually fix it.