If your boiler has no power (a blank display, no lights and no response to the controls), the cause is usually outside the boiler: a power cut, the fused spur switched off, a blown fuse in that spur, or a tripped switch at the consumer unit. You can check all of those safely yourself, but if power is reaching the boiler and it still stays dead, or the electrics trip every time it is switched on, the fault is inside the boiler and needs a Gas Safe registered engineer.

First, what exactly are you seeing?

“No power” can mean slightly different things, and each one points somewhere different.

What you see	Most likely cause
Boiler dead and other lights or sockets off too	Power cut, or a main switch or RCD tripped at the consumer unit
Boiler dead, everything else in the house working	Fused spur off, blown spur fuse, the boiler’s own switch off, or a circuit breaker for the heating tripped
Boiler dead and the heating timer or programmer dead too	The supply to the whole heating system, often the same fused spur
Power returns, but the electrics trip when the boiler starts	A fault in the boiler or its wiring, sometimes water reaching electrical parts
Spur has power, fuse is fine, boiler still dead	A fault inside the boiler: internal fuse, control board or wiring
Display lit but boiler will not fire	Not a power problem. See our guide to a boiler not firing up

If you would rather not work through it, our boiler repair service covers all the major brands and the phone is answered 24 hours a day, 7 days a week.

Check these first

Work through these in order. They are all safe for a homeowner and none of them involve opening the boiler.

1. Is it a power cut? Try a light and a socket. If nothing works, check whether your neighbours have power. In Great Britain you can call 105 free to report or check a power cut with your local network operator.
2. The boiler’s own switch. Many boilers have an on/off button or dial on the front. Check it has not been knocked off.
3. The fused spur. Boilers are normally wired through a switched fused connection unit, usually on the wall near the boiler. Make sure the switch is on. Many have a small indicator light that shows when power is getting through.
4. The fuse in the spur. If the spur has a fuse carrier, switch it off, pull out the carrier and check the fuse, or simply swap it for a new one of the same rating. Manufacturers such as Ideal specify a 3A fuse for their boilers, and your installation manual will say. If the new fuse blows as soon as the boiler starts, stop. There is a fault that needs finding.
5. The consumer unit. Look for a circuit breaker or RCD that has tripped (it will sit in a different position from the rest). Reset it once. If it trips again straight away, or trips when the boiler starts up, leave it off.
6. The controls. If the boiler has power but nothing happens, check the timer and thermostat. After a power cut, clocks often reset, and wireless thermostats and smart hubs may need to reconnect. Replace thermostat batteries if the display is weak or blank.
7. Reset once power is back. Some boilers come back with a fault showing after a cut. Press reset as your user guide describes, once or twice at most.

Common causes

Cause	What you might notice	Can you fix it yourself?	What the engineer does
Power cut	Whole house or street off	Wait for it to come back, then reset the boiler	Nothing needed unless the boiler stays dead afterwards
Fused spur switched off	Everything else works, spur light off	Yes, switch it back on	Nothing needed
Blown spur fuse	Spur on but no power to the boiler	Yes, replace with the same rating once	Finds out why it blew if it happens again
Tripped breaker or RCD	One switch down at the consumer unit	Reset once only	Tests the boiler and wiring for the fault causing the trip
Leak reaching electrical parts	Tripping, water inside or under the boiler	No, leave the power off	Finds and fixes the leak, dries and tests the electrics
Blown internal fuse	Power at the spur, boiler still dead	No	Tests the fuse and finds the cause before replacing it
Failed control board or display	Power reaching the boiler but no display or response	No	Tests the board and replaces it if it has failed
Damage after a power surge	Boiler dead after a storm or supply fault	No	Tests the board and components for damage
Loose or damaged wiring	Intermittent loss of power, burning smell	No	Makes the wiring safe and repairs it

What an engineer will check

A Gas Safe engineer will normally:

• Isolate the boiler safely and confirm whether mains voltage is reaching the spur and the boiler’s terminals.
• Check the wiring between the spur, the boiler and the controls, including any wiring centre for the heating system.
• Test the boiler’s internal fuses, and if one has blown, find what blew it before fitting a new one.
• Look for water leaks inside the case that could be reaching electrical parts.
• Test the control board, display and other electrical parts.
• Once power is restored, run the boiler through heating and hot water and check it is working safely.

If the problem is clearly in the house wiring rather than the boiler, for example a circuit that keeps tripping with the boiler disconnected, an electrician is the right person for that part. Our electrical fault finding service covers that.

Frost risk while the boiler is off

Modern boilers have frost protection, but it only works while the boiler has power. Ideal’s user guides, for example, make the point that frost protection depends on the power supply staying on. If your boiler loses power in freezing weather, get it back on as soon as you can. If the boiler also shows a fault in cold weather after the power returns, check the condensate pipe outside, as described in our frozen condensate pipe guide.

Repair or replace?

Most “no power” call-outs are simple: a fuse, a switch or a tripped circuit. When the fault is inside the boiler, the usual repair is a fuse or a control board. A board is one of the dearer parts, so on an older boiler that has had several recent repairs, it is worth weighing up a replacement. We will give you an honest view and a quoted price before any work goes ahead.

What it costs with Vantage

In normal working hours there is no call-out fee. Gas faults start with a fixed-price Gas Safe diagnostic visit, and if we can fix it on the same visit, part of that diagnostic charge comes off the repair. After the first hour, time is charged in half-hour steps, and parts are quoted before we fit them. Evening, weekend and overnight visits are charged at the out-of-hours rates. Every rate is published on our prices page, so you know what you will pay before we arrive.

Frequently asked questions

Will my boiler work without electricity?

No. A modern gas boiler needs electricity to run its controls, fan, pump and ignition, so during a power cut you will have no heating and no hot water from it. Once power returns, most boilers restart on their own, although some need a reset.

What fuse does a boiler need?

Most boilers are supplied through a fused spur, and manufacturers such as Ideal specify a 3A fuse. Check the rating on the old fuse or in your boiler manual and always replace like for like. Never fit a bigger fuse to stop one blowing.

Why has my boiler lost power after a power cut?

The boiler may have locked out when the power dropped, the clock on the timer may have reset, or a surge when the supply came back may have tripped a switch or damaged a part. Check the consumer unit, the fused spur and the timer settings, then reset once. If it stays dead with power at the spur, call an engineer.

Why does my boiler keep tripping the electrics?

A boiler that trips the RCD or a breaker has a fault somewhere in the boiler, its wiring or its controls. A water leak reaching electrical parts is a common cause. Leave the power off at the spur and have a Gas Safe engineer find the fault.

Can an electrician fix a boiler with no power?

An electrician can check the supply up to the boiler, including the circuit, the spur and the wiring to the heating controls. Anything inside the boiler case, including its internal fuses and control board, must be dealt with by a Gas Safe registered engineer.

When to call an engineer

If the power is reaching the boiler and it still stays dead, a fuse keeps blowing, or the electrics trip whenever the boiler starts, it needs a Gas Safe engineer. We are Gas Safe registered (956889), based in Stevenage, and cover Hertfordshire, Bedfordshire and Cambridgeshire, with 24/7 emergency cover. Book through our boiler repair page or call 01462 506374.