Batteries with a heat pump
Short answer
It can be one of the better pairings. EST's July 2026 modelling found batteries save more alongside a heat pump than alongside solar, because the battery lets the heat pump run on cheap-rate electricity. But winter heat demand is large: check that battery size and inverter power cover the heat pump's peak draw through the 4-7pm peak window.
Last checked 24 September 2026 · 7 sources
What should I know before deciding?
EST: heat pump + battery + solar up to ~£800/yr saving; best combinations over £1,000; moving to a heat-pump or dynamic tariff alone can cut heating cost by up to £330. Cosy Octopus (heat pump required) has several cheap windows a day, which suits smaller batteries recharged twice daily. EST: using a battery for regular electric heating needs one about three times bigger. Size on winter kWh during peak hours, not annual average; inverter kW limits how much of a 3-5 kW heat pump draw the battery can cover.
Should I size my battery for a heat pump or electric car?
Plan for them, but model them separately. The MCS self-consumption method excludes heat pumps and EVs, which can double winter use. A heat pump raises evening and winter demand; charging an EV from the home battery rarely pays unless using spare solar. Charger wiring relative to the battery's meter clamp matters.
Large EV/heat-pump loads can also exceed inverter power and main fuse when grid-charging.
What backup reserve should I set, and what happens below it?
The reserve is the charge kept back for power cuts; the battery stops normal daily discharge when it reaches it. Many owners use 10-20%, raising it before storms. Tesla's Storm Watch does this automatically in the UK. If a Powerwall falls below 10% in an outage it goes to standby, and below 5% it holds energy to restart from solar.
Reserve trades savings for resilience: every kWh reserved is not used to avoid peak import. Tesla UK support: under 10% Powerwall enters standby and stops powering the home; if an outage starts under 5% the home loses power immediately; with solar it tries to recharge hourly 8am-4pm. Storm Watch (Tesla, available in the UK) charges to 100% from the grid ahead of severe-weather alerts, then returns to your normal mode.
What to do next
Use your own half-hourly electricity data where possible. Compare usable kWh, kW, tariff rules and warranty terms before buying.
Sources
- Energy Saving Trust — energysavingtrust.org.uk/renewable-technologies-what-really-cuts-energy-bills/
- Octopus Energy — octopus.energy/policies/smart-tariffs-terms-and-condition/
- MCS — mcscertified.com/wp-content/uploads/2022/04/MGD-003-Solar-PV-Self-Consumption-I…
- Tesla — www.tesla.com/en_gb/support/energy/powerwall/own/best-practices-during-power-cu…
- Tesla — www.tesla.com/support/energy/powerwall/mobile-app/storm-watch
- Energy Saving Trust — energysavingtrust.org.uk/advice/battery-storage/
- Tesla — www.tesla.com/en_gb/support/energy/powerwall/mobile-app/storm-watch
Last checked: 24 September 2026