Usually, no. A modern boiler may burn gas, oil or LPG, but it still needs electricity for its controls and for the heating system to work. The public GOV.UK Prepare guidance is blunt: boilers will not work without power.
In England, Scotland and Wales, call 105 free to report the cut. In Northern Ireland, call NIE Networks on 03457 643643. Do not open the boiler casing or improvise a power supply. Your exact restart procedure depends on the model, so keep the manual somewhere you can find it without the internet.
Why does a boiler need electricity if it burns fuel?
The flame is only one part of a modern heating system. Its programmer, thermostat, electronic safety controls and the equipment that moves heated water all depend on electricity. When the mains supply disappears, the safe normal result is no central heating and no newly heated water.
That answer applies to most domestic boilers, whatever is in the fuel tank. Gas, oil and LPG describe the fuel. Combi, system and heat-only describe how the heating and hot water are arranged. Energy Saving Trust explains those distinctions; the practical power-cut answer is below.
| Boiler or system | Heating during the cut | Hot water during the cut |
|---|---|---|
| Combi boiler | Stops | No new hot water: there is no cylinder |
| System boiler | Stops | Water already stored in the cylinder may remain usable |
| Heat-only or regular boiler | Stops | Stored cylinder water may remain usable; delivery depends on the system |
| Oil boiler | Normally stops | Depends on whether it is combi or has a cylinder |
| LPG boiler | Normally stops | Depends on whether it is combi or has a cylinder |
These are the usual arrangements, not a promise for every installation. Pumps, valves, cylinders and controls differ. Check the manual or ask your installer what happens in your home.
What happens to a combi boiler in a power cut?
Will a combi boiler still give me hot water?
Normally, no. A combi heats water on demand and has no hot-water cylinder. Energy Saving Trust says the heating and hot water come directly from the boiler, so when the boiler loses power it cannot make more hot water for the taps.
You may get a brief bit of warmth from water already sitting in the pipework. That is residual heat, not the boiler carrying on. Avoid repeatedly opening taps to test it; you will simply use what little warmth remains, and the boiler won’t be any more persuaded.
Does the gas supply make any difference?
Having gas at the meter does not restore the electrical controls. Do not try to light a modern boiler by hand, bypass an interlock or remove its cover. If you can smell gas, leave the appliance alone and call the National Gas Emergency Service on 0800 111 999 (NHS). In Northern Ireland, it’s 0800 002 001 (HSENI).
What happens to a system or heat-only boiler?
Can I use water that is already in the cylinder?
Often, you can use at least some water heated before the cut. A system boiler has a separate hot-water cylinder. A heat-only boiler has a cylinder too, usually with extra cold-water header tanks. A well-insulated cylinder holds heat rather than producing it, so the stored water will gradually cool (Energy Saving Trust).
Whether hot water reaches a particular tap can depend on your plumbing, valves, water supply and any electric pump. Use what is available sparingly. Do not assume an electric immersion heater will help: it needs mains electricity as well, unless it is connected to a properly designed backup supply.
Will the radiators stay warm?
They may remain warm for a little while, but the system is no longer adding heat. How quickly rooms cool depends on the weather, insulation and the building itself. Close curtains and doors to unused rooms, add layers early and bring everyone into one room if the home becomes cold (Prepare).
Will an oil boiler work in a power cut?
Does a full oil tank keep the heating on?
No. The oil is the fuel, not the electrical supply. OFTEC’s liquid-fuel troubleshooting guidance tells households to check that the heating and hot-water system has electricity. It also warns that a programmer or timer may return to default settings after a cut.
Oil systems vary. Some are combis; others use a cylinder. That changes whether previously heated water is stored, but it does not make the normal central heating independent of mains power. After electricity returns, check the time and schedule before assuming there is a fault.
Will an LPG boiler work in a power cut?
Does LPG behave differently from mains gas?
Not in the way that matters here. LPG is stored at the property rather than arriving through the gas grid, but the boiler and central-heating controls still normally rely on electricity. The Energy Saving Trust boiler guide treats LPG as a fuel option and separately explains combi, system and heat-only arrangements.
So, check both labels: your fuel tells you what the boiler burns; the system type tells you whether there is stored hot water. The manual tells you the model-specific restart steps.
What should I do in the first 10 minutes?
Is it a power cut or a boiler fault?
Look at nearby homes or street lights. Check whether other electrical items in your home have stopped. If the whole area is off, report it to the electricity network rather than calling a boiler engineer first (Prepare).
- Use a battery or wind-up torch, not candles.
- Call 105 in England, Scotland or Wales, or 03457 643643 in Northern Ireland.
- Leave the boiler casing, wiring and fused connection alone.
- Close curtains and doors to unused rooms. Put on several thin layers and use blankets.
- Check on anyone who is older, very young, unwell or living alone.
- Keep one light switched on so you notice when power returns.
How do I stay warm safely if the cut lasts?
The UK Chief Medical Officers advise several thin layers, gentle movement, closed curtains and gathering in one room during severe cold. Never use a barbecue, camping stove or generator indoors, in a garage, shed or tent. A generator must stay outdoors, well away from doors, windows and vents (UK CMO guidance).
A flask of hot water filled while you still had power is worth its weight in gold here: hot water bottles, a cup of tea, and a small, well-earned sense of smugness.
Fit an audible carbon-monoxide alarm in every room containing an appliance that burns gas, oil, coal or wood. The NHS says carbon monoxide has no colour or smell. If an alarm sounds or anyone develops headache, dizziness, sickness, weakness, confusion, chest pain or breathlessness, get outside and seek medical help.
What should I do when the power comes back?
Should the boiler restart by itself?
Many systems restart, but behaviour varies by model. Give the boiler a few minutes, then check the display, thermostat, clock and programmed times. Oil-system timers may have reset to factory defaults after the outage (OFTEC).
Follow the user manual before pressing reset. Do not remove the casing, touch internal electrics or repeatedly reset a boiler that locks out. If it still will not run, note any fault code and contact a suitably qualified engineer. For gas or LPG work, use Gas Safe; for oil heating, use an OFTEC-registered technician.
People who need extra help
If cold poses a particular risk, make a plan before winter with the person’s clinician, carer or support network. In Great Britain, the free Priority Services Register can provide advance notice of planned cuts and extra help in an emergency. Energy suppliers and network operators keep registers, so contact both (Ofgem). A register does not guarantee continuous electricity. If phones are down, arrange for a trusted person to visit rather than relying only on a call.
If you live in Northern Ireland, Scotland or Wales
In Scotland and Wales, report a power cut on 105 and use the Great Britain Priority Services Register arrangements. In Northern Ireland, call NIE Networks on 03457 643643. Northern Ireland uses Customer Care Registers for people who depend on electricity or water for daily care; the register prioritises contact and advance warning rather than guaranteeing supply (nidirect). Oil heating is particularly common in Northern Ireland, but the same advice applies: check the electricity supply and programmer after the cut, then follow the boiler manual.
We’re putting together an Essentials Kit: the non-food essentials from the Prepare list in one bag, with a card saying which water and tins to add. Join the list to hear when it’s ready.
Sources
- GOV.UK Prepare, Power cuts: https://prepare.campaign.gov.uk/be-informed-about-hazards/power-cuts/
- Energy Saving Trust, Boiler types explained: https://energysavingtrust.org.uk/advice/boilers/
- OFTEC, Trouble shooting tips for liquid-fuel heating: https://www.oftec.org/consumers/trouble-shooting-tips/
- UK Chief Medical Officers, Keeping warm or cool in extreme weather: https://www.gov.uk/government/publications/public-health-advice-from-uk-cmos-during-a-national-power-outage/keeping-warm-or-cool-in-extreme-weather-scripts-for-broadcast-media
- NHS, Carbon monoxide poisoning: https://www.nhs.uk/conditions/carbon-monoxide-poisoning/
- Ofgem, Priority Services Register: https://www.ofgem.gov.uk/your-energy-supply/how-manage-your-energy-supply/join-your-suppliers-priority-services-register
- nidirect, Care registers: https://www.nidirect.gov.uk/articles/care-registers
- HSENI, Carbon monoxide dangers: https://www.hseni.gov.uk/news/carbon-monoxide-dangers-heating-appliances-and-generators-used-indoors