No. A heat pump needs electricity, so it stops during a power cut. That is true for air source and ground source systems. Your radiators or underfloor heating may stay warm for a while, and a hot-water cylinder may hold water heated earlier, but the heat pump cannot add more heat until power returns.
Report the outage on 105 in England, Scotland and Wales, or call NIE Networks on 03457 643643 in Northern Ireland. SSEN says heat pumps normally resume when power returns, but models vary. Check your manual or installer rather than guessing at reset buttons.
What exactly happens to a heat pump in a power cut?
Does an air source heat pump stop completely?
Normal heating stops. The unit, controls and heating system all depend on electricity. GOV.UK Prepare lists heat pumps among the household systems that will not work without power.
The outdoor unit being silent is therefore expected during an outage. It does not mean the heat pump has been damaged. SSEN says low-carbon equipment is designed with safety features and should be ready to work again after supply is restored.
What about a ground source heat pump?
It stops too. The buried pipework may still contain available heat, but the system cannot collect, upgrade and distribute it normally without electricity. The same is true of a water source heat pump. The source of heat has not vanished; the powered equipment needed to use it has paused.
Will radiators or underfloor heating stay warm?
For a short time, because the building and heating water have stored some heat. That warmth will fade. Heat pumps often run for longer at lower flow temperatures than fossil-fuel boilers, so radiators may not have started fiercely hot in the first place (Energy Saving Trust).
How quickly your home cools depends on outdoor temperature, draughts, insulation and the building’s thermal mass. It is not useful to promise a number of hours. Start keeping heat in early rather than waiting until everyone feels cold.
Will I still have hot water?
Does a heat-pump cylinder keep water hot?
Usually, a domestic heat pump stores hot water in a cylinder rather than producing it instantly like a combi boiler. Water heated before the cut may therefore remain warm and usable for a while. An insulated cylinder slows heat loss; it does not keep reheating itself (Energy Saving Trust).
Whether the water reaches your taps without power depends on the installation. Some systems rely on powered controls or pumps. Use stored hot water sparingly and ask your installer in advance what your particular arrangement does.
Will the immersion heater work instead?
Not from an ordinary mains circuit. An immersion heater is electrical, so it stops in the same cut. Some homes have batteries or another backup arrangement, but the installer must confirm which circuits are supported and whether the system can safely carry the load.
Will solar panels or a home battery run my heat pump?
Do solar panels work when the grid is down?
Ordinary grid-connected solar normally shuts down in a cut. This prevents the system sending electricity into lines that engineers may be repairing. SSEN says solar should usually restart automatically after mains power returns (SSEN).
Sunshine outside is therefore not proof that the sockets are live. An installation specifically designed for backup operation is different, but its behaviour depends on the inverter, controls and circuits selected by the installer.
Does a home battery make the heat pump outage-proof?
No. SSEN says batteries usually switch off with the grid unless they have a backup or “island mode”, and that mode may power only parts of the home. A heat pump can be a substantial load, so a battery that keeps lights and a router running may not run the heating.
Ask your installer four plain questions:
- Does this system operate when the grid fails?
- Which circuits are backed up?
- Is the heat pump one of them?
- What runtime should we expect at winter load and at the battery’s current condition?
Runtime varies with battery size, charge, age, outside temperature and household demand. Treat the installer’s answer as system-specific, not a general promise.
What should I do in the first 10 minutes?
How do I check that it is a power cut?
See whether neighbours or street lights are off, and check other electrical items in your home. If the area is affected, report the cut to the electricity network. Your energy supplier sells the electricity; the network operator repairs the local wires (Prepare).
- Get a battery or wind-up torch. Torches are safer than candles.
- Report the cut on 105, or 03457 643643 in Northern Ireland.
- Leave the heat-pump casing and electrical isolators alone unless your manual specifically instructs otherwise.
- Close curtains and doors to rooms you are not using.
- Add thin layers and blankets before the home becomes very cold.
- Check on older people, babies, young children and anyone with a health condition.
- Keep one light switched on so you know when electricity returns.
If a planned cut is coming, charge phones and power banks, heat the home normally beforehand and make sensible use of the hot-water schedule. Do not raise settings far beyond normal in an attempt to turn the house into a storage heater with carpets.
How do I stay warm if the outage lasts longer?
The UK Chief Medical Officers’ guidance recommends several thin layers, blankets, gentle movement and gathering in one room during severe cold. Close curtains when it gets dark and shut windows and doors in rooms you are not using. Keep required ventilation clear.
Never use a barbecue, camping stove or generator indoors, in a garage, shed or tent. Never run a vehicle engine in a garage. These can produce carbon monoxide, which you cannot see or smell. Use only heating equipment designed for indoor use, follow its instructions and keep a working CO alarm in every room containing an appliance that burns gas, oil, coal or wood (NHS).
What happens when the power comes back?
Will the heat pump restart automatically?
Usually, according to SSEN, but there may be a short safety delay. Model behaviour differs. Wait, then check the controller for a normal status or fault message. Confirm that heating and hot-water schedules are correct. If the unit remains off, follow the exact manual or contact the installer.
Do not repeatedly switch the supply off and on. If solar, battery or smart controls are part of the system, check each according to its own instructions.
People who need extra help
If losing heat would create a medical risk, agree a plan with the person’s clinical or care team before winter. In Great Britain, join both your energy supplier’s and network operator’s Priority Services Registers. Support can include advance warning of planned cuts and priority help in an emergency (Ofgem). It does not guarantee continuous power. Keep backup plans for powered medical equipment separate from the heating plan.
If you live in Northern Ireland, Scotland or Wales
Scotland and Wales use 105 and the Great Britain Priority Services Register arrangements. Northern Ireland uses NIE Networks on 03457 643643 and calls its equivalent schemes Customer Care Registers. These prioritise contact and notice of planned outages for people who depend on electricity or water for daily care (nidirect). Heat-pump restart behaviour still depends on the model and installation in every nation.
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/
- SSEN, Planned power cuts and low-carbon technology: https://www.ssen.co.uk/power-cuts-emergencies/planned-power-cuts/
- Energy Saving Trust, Heat pump installation guide: https://energysavingtrust.org.uk/heat-pump-installation-a-step-by-step-guide?loc=scotland
- 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