A heat pump can be one of the largest electrical loads in a home, so it is sensible to ask: can batteries run heat pumps? Yes, they can, but the useful answer depends on the size of the heat pump, the battery’s power output, the heat retained by the property and what you expect during a power cut. A well-designed system can reduce electricity costs and provide valuable resilience. It is not, however, a guarantee of unlimited heating from a small home battery.
Can batteries run heat pumps in a typical UK home?
In normal day-to-day operation, a battery can supply some or all of a heat pump’s electricity demand. This is particularly useful when the battery has been charged from surplus solar generation or during a cheaper off-peak electricity period. The battery discharges when household demand is higher or grid electricity costs more, helping you use more of your own energy.
The challenge is that heat demand is seasonal. A heat pump usually uses most electricity on cold, dark winter days, when solar generation is lower and the home may need heating for longer. In summer, a solar battery may regularly fill. In winter, it may be more valuable for covering evening household use, short heating periods or carefully planned tariff charging.
That does not make battery storage a poor match for a heat pump. It simply means the system should be specified around realistic priorities: bill savings, solar self-consumption, essential backup, or full house backup. Each requires a different approach.
Battery capacity and power are not the same thing
Two figures matter when considering a battery for a heat pump. Capacity is measured in kilowatt-hours (kWh), while power is measured in kilowatts (kW).
Capacity tells you how much energy the battery stores. A 10 kWh battery could, in simple terms, supply a continuous 2 kW load for around five hours. Actual results will vary because the battery may have a usable capacity limit, other appliances will be running, and energy is lost in conversion.
Power tells you how quickly the battery can deliver electricity. This is vital for heat pumps. A battery may have enough stored energy for several hours but still be unable to support the heat pump if its inverter cannot provide the required output, particularly when other loads such as kettles, ovens, showers or EV charging are in use.
For example, a heat pump might draw 1.5 kW while maintaining temperature in mild weather, then need substantially more at colder times or during hot-water production. Starting currents and electrical characteristics also need checking. The heat pump, battery inverter, consumer unit and protective devices must work together safely.
A competent electrical and renewable-energy installer will assess both capacity and output rather than recommending a battery based on kWh alone.
How long can a home battery run a heat pump?
There is no single number, but a few practical examples show why property-specific design matters.
If a heat pump is drawing an average of 2 kW and the battery has 10 kWh of usable stored energy, the theoretical maximum is about five hours with nothing else switched on. In reality, lighting, refrigeration, broadband equipment, cooking and other household loads reduce this time. A 13.5 kWh battery may offer more breathing room, but it still cannot power continuous heating indefinitely through a cold night without charging.
A well-insulated home may need less heat to maintain a comfortable temperature, extending battery runtime. A poorly insulated property, or one set to a high internal temperature, will place greater demand on the system. Underfloor heating, radiator sizing, hot-water schedules and weather compensation settings can all influence how hard a heat pump has to work.
The most useful question is often not, “How long will it run?” but, “What do I need it to achieve?” Covering peak-price electricity for a few evening hours is a very different requirement from maintaining heating throughout a multi-hour power cut.
Hot water can change the calculation
Domestic hot-water heating can create a noticeable increase in electrical demand. When a heat pump heats a cylinder, it may run for a sustained period. If an immersion heater operates as a backup or for legionella protection, demand can rise much further, often beyond what a modest battery should be expected to supply for long.
Controls can help. Scheduling hot-water production for solar-rich periods or low-cost tariff windows can protect battery capacity for the evening. This needs to be planned around your household routine, not left to assumptions.
Using solar, batteries and heat pumps together
Solar panels, battery storage and a heat pump can work very effectively as an integrated system. Solar electricity can run household loads directly, charge the battery, and contribute to heat-pump operation. A battery then stores energy for later use rather than exporting all surplus generation to the grid.
However, winter expectations need to stay realistic. Solar production falls precisely when space-heating demand rises. Even a large solar array may not generate enough in midwinter to fully charge a battery and meet heating needs every day. The grid remains an important energy source for most homes.
Time-of-use tariffs can make the combination more compelling. A battery can charge during cheaper overnight periods and discharge during expensive periods, subject to tariff rules and system settings. With thoughtful controls, the heat pump can also be encouraged to heat the home or hot-water cylinder when electricity is lower-cost.
This approach is about reducing the cost of imported electricity, not necessarily eliminating it. The savings depend on your tariff, heating system, solar generation, battery size and how the household uses energy.
Can a battery keep a heat pump running in a power cut?
This is where many homeowners are caught out. Not every battery installation provides power during a grid outage. Some systems are designed only for energy storage and switch off when the grid fails, as required for safety. To keep selected circuits live, the installation needs an emergency power supply, commonly called EPS, and the right changeover arrangement.
Running a heat pump during an outage requires more careful consideration than backing up lights, sockets, refrigeration and Wi-Fi. The battery and inverter must support the heat pump’s required output, and the backup arrangement must be designed to handle the load safely. In some homes, it makes more sense to prioritise essential circuits and preserve power rather than run all heating equipment without limits.
Full house backup can be possible with appropriately sized equipment and a detailed load assessment. It should never be assumed from a battery brochure. Larger systems may need multiple batteries, higher-output inverters, dedicated backup boards and changes to the existing electrical installation.
For households where resilience matters, a clear backup plan is more valuable than a headline battery size. Decide what must stay on: perhaps heating controls, selected heating operation, refrigeration, lighting, communications and security. Then build the system around that priority.
What size battery is right for a heat-pump home?
There is no universal battery size, but the following factors shape a sensible recommendation:
- The heat pump’s electrical input at normal and cold-weather conditions.
- Your daily electricity use, including cooking, EV charging and hot-water demand.
- Solar array size, roof orientation and expected winter generation.
- Whether the goal is tariff savings, solar storage, outage protection or full house backup.
- The battery inverter’s continuous and peak power rating.
- The condition and capacity of the existing consumer unit, earthing and electrical supply.
A smaller battery may be a sensible first step for solar self-consumption and evening electricity savings. A larger battery bank can offer greater flexibility, but it costs more and needs enough regular charging opportunity to justify the investment. Oversizing without considering actual usage can leave capacity underused for much of the year.
For some properties, upgrades beyond the battery are equally important. Better insulation, correct heat-pump commissioning, improved heating controls and a suitable hot-water strategy may reduce consumption more effectively than simply adding storage.
Safe design matters as much as the equipment
A battery, heat pump and solar system connect high-power equipment across your home’s electrical installation. The quality of design and installation affects performance, safety and future reliability.
Before work begins, the installer should understand your supply arrangement, main fuse capacity, consumer unit, earthing, cable routes, heating equipment and intended backup loads. They should also explain what happens in a power cut, which circuits are supported and any limits on high-demand appliances.
Home EESS approaches these projects as complete electrical systems, not as isolated products. That means matching modern solar and storage technology with sound electrical workmanship, clear operating guidance and long-term support.
A battery will not turn a heat pump into an off-grid heating system through every British winter. It can, however, help a well-planned home use cheaper and self-generated electricity more effectively, while giving you a measured level of resilience when the grid is unavailable. The right next step is a site-specific assessment that starts with how you live, heat your property and want your home to perform when power matters most.
