Choosing a Home Battery for a Home With a Heat Pump and an EV
- Start with the tariff. The Energy Saving Trust says tariff matters as much as the technology.
- Its modelling found a heat pump, solar and battery together cut bills by about £800 a year on average, but that figure is for the combined system, not the battery alone.
- Most EV batteries are far larger than a home battery, so the home battery will not cover a full car charge on its own.
- Compare power (kW) as well as capacity (kWh), because heating and charging draw a lot at once.
- Ask installers to show how the battery, heat pump and car charger will be controlled together.
A heat pump and an electric car both turn your electricity bill into your main energy bill, which makes a battery more interesting and the buying decision more specific. The tariff you choose matters at least as much as the battery.
Why the tariff comes first
The Energy Saving Trust's analysis of low carbon technology combinations is clear that swapping gas for a heat pump on a standard flat-rate tariff often saves little, while a heat pump tariff or a dynamic tariff that changes every 30 minutes can change the picture. It describes the savings as scenario-based, built from data on 546 homes.
For a battery, that means you buy the tariff and the battery as a pair. A battery that can charge when electricity is cheap and feed the heat pump later is the use the Trust highlights. Our explainer on dynamic energy contracts covers the mechanics.
What the research does and does not say about batteries
The Trust reports that a heat pump, solar panels and a battery together cut bills by about £800 a year on average, and by more than £1,000 in the best cases. That figure belongs to the whole system. It does not tell you what a battery adds on its own, and the article gives no standalone battery saving.
It also suggests a battery paired with a heat pump can be better value than one paired with solar alone, because it depends on charging cheaply and using the stored energy for heating. Treat that as a reason to model your home, not a promise.
An EV changes the sizing question
Many EV batteries are several times larger than a typical home battery. A home battery can help with a short top-up or an evening charge, but it will not replace cheap overnight charging for the car. Our guide on charging an electric car from a home battery goes through what is realistic.
Because a heat pump and a car charger can run together, look at the battery's continuous power in kW, not only its capacity. A large battery with a modest power rating can still leave the grid doing most of the work at peak moments.
List your loads
Note the heat pump's electrical rating, the car charger's power and how often you charge.
Pick the tariff
Choose the tariff you would actually use, then test the battery against it.
Size for power and energy
Use the home battery calculator and compare kW and kWh together.
Check the controls
Ask how the battery, heat pump and charger will be coordinated, and by whose software.
Do not size for the car
If the battery is sized around the EV, it may sit mostly empty after one charge. Size around the household loads and treat the car as a bonus.
Questions to ask installers
The Trust recommends getting at least three quotes from MCS-certified installers. When you have them, put the same questions to each, and compare the answers rather than the headline specification.
- Will the battery work with my chosen tariff and my heat pump's schedule?
- Can it charge from the grid on a cheap rate, and can I set that myself?
- What happens to the battery during a long heat pump cycle in winter?
- Is the car charger controlled by the same app, or separately?
Common questions
Do I need a battery if I have a heat pump?
Not necessarily. The Energy Saving Trust says tariff choice matters as much as the equipment. A battery helps mostly when it lets you move electricity use to cheap periods.
Can a home battery charge my EV?
It can supply some of the charge, but many EV batteries are much larger than a home battery, so it will not usually cover a full charge.
Is the £800 a year saving a guarantee?
No. It is an average from the Energy Saving Trust's scenarios for a combined heat pump, solar and battery system. Your result depends on your home and tariff.
Related guides
Want to know which battery size fits your home?
Use our free calculator to get a size, savings and payback estimate.