Can a Solar Battery Run a Heat Pump
Yes, it can. They are among the most battery‑friendly heating systems you can buy. They run on electricity, draw power steadily, and work well with a hybrid inverter, so the battery can supply them at night, during a blackout, or when electricity rates are high.
The key point most articles miss is the difference between a solar panel and a solar battery. Panels only produce during the day. The battery stores that daytime solar power and lets it keep running after dark. That is exactly where the unit draws most of its energy — overnight heating is the reason owners pair the two together.
A typical air‑source heat pump (ASHP) pulls 1.5–3 kW while running in mild weather, because it moves 3–4 units of heat for every unit of electricity it uses (a COP of 3–4). In freezing weather the COP drops toward 2, and the draw can rise to 3–4 kW. Those numbers drive every runtime and sizing decision below.
How Long Can a Solar Battery Run a Heat Pump
Use this simple formula:
Runtime (hours) = usable battery kWh ÷ the pump's draw (kW)
LiFePO4 solar batteries allow a 90% depth of discharge, so a 15 kWh battery gives you about 13.5 kWh of usable energy. Divide that by a 2.5 kW average draw and you get roughly 5 hours.
| Battery size | Usable energy (90% DoD) | Runtime at 2.5 kW (mild weather) | Runtime at 3.5 kW (cold weather) |
|---|---|---|---|
| 10 kWh | 9 kWh | ~3.5 h | ~2.5 h |
| 15 kWh | 13.5 kWh | ~5.5 h | ~4 h |
| 20 kWh | 18 kWh | ~7 h | ~5 h |
| 30 kWh | 27 kWh | ~11 h | ~7.5 h |
A mini‑split draws less — often 0.8–2 kW — so the same battery lasts roughly twice as long. Run your own numbers with your system's nameplate draw and the table above, because every home is different.
How Many Solar Panels Do I Need for a Heat Pump
EnergySage's research puts a whole‑home air‑source heat pump at 9–13 solar panels for the average home. The panel count depends on how much it runs, your climate, and the panel wattage.
For the battery question, what matters is this: the panels have to charge the battery and cover the daytime heating load.If you are unsure how large your solar array needs to be, start with our guide to solar system sizing. A common rule is to add 2–3 panels on top of the battery‑charging array for all‑day running. If it only runs a few hours at night, the battery does most of the work and the panels can stay smaller.
How to Size a Solar Battery for a Heat Pump
Follow these four steps in order:
- Step 1 — Measure the unit's winter energy use. Read your inverter or monitoring app during the coldest week. A typical home uses 15–30 kilowatt‑hours per day for heating in winter. Cold climates sit at the top of that range.
- Step 2 — Decide how many hours you want on battery. Night heating from 7 p.m. to 7 a.m. is 12 hours. Most owners target 6–10 hours on the solar battery, because daytime heat runs off the panels directly.
- Step 3 — Apply the formula. Daily battery energy = hours × average draw. For 8 hours at 2.5 kW that is 20 kWh of usable energy, which means a 22–24 kWh battery at 90% DoD.
- Step 4 — Round up, and size the bank for the biggest load, not the car. As one installer told The Independent: "I would size it around a heat pump and not a car. There's no need to oversize your home battery." If a future EV charger may join the system, plan the battery bank now — expanding later is easy if your system supports parallel batteries, but sizing correctly from day one is cheaper.
How Much Does a Solar Battery for a Heat Pump Cost
In 2026, LiFePO4 solar batteries sell for roughly 150 per kWh before installation. A few real price points from a manufacturer price list:
| Battery | Typical list price |
|---|---|
| 15–16 kWh home battery | 2,100 |
| 20 kWh battery | ~$2,100 |
| 30 kWh system | ~$3,100 |
Add 2,000 for a hybrid inverter and installation if you are building from scratch, or less if you already have a solar system. Against that, pairing solar storage with an electric heating system typically cuts winter heating bills by 50–70% where electricity rates are high — which is why most owners treat the battery as part of the heating budget, not an extra.
4 Common Mistakes When Pairing a Heat Pump with Solar Battery
-
Undersizing the battery.
A 10 kWh battery disappears in 3 hours on a cold night. Homeowners who buy small first end up buying again.
-
Ignoring the defrost cycle.
In cold weather, the unit runs a defrost cycle that spikes power draw for 5–10 minutes. Your inverter must handle that peak, or it will trip and stop charging.
-
Forgetting winter performance.
Cold weather cuts both battery capacity and the pump's COP at the same time. See our winter storage guide for charging and protection tips.
-
No soft start on the compressor.
A soft starter cuts the compressor's startup surge, so a smaller battery and inverter can handle it. Cheap insurance for off‑grid setups.
FAQ
Is it cheaper to leave a heat pump on 24/7
Usually yes — they are more efficient when they run steadily than when they cycle on and off all day. But with a solar battery, it can be even cheaper to run it hard while the sun is out, charge the battery, and let it carry the evening.
How long will a 20kWh battery run a heat pump
About 5–7 hours at a typical 2.5–3.5 kW draw, since 90% of 20 kWh is 18 kWh of usable energy. With a mini‑split at 1 kW, the same battery lasts up to 18 hours.
Can I run a heat pump off‑grid with a solar battery
Yes, if the array and battery are sized for your worst winter week. You need enough panels to recharge the battery during short winter days, plus a generator or second battery bank as a reserve. Off‑grid heating in cold climates is the hardest sizing case — plan for 3+ days of autonomy, not one night.
Do I need a bigger battery for cold climates
Yes. Cold weather lowers the battery's usable capacity and raises the unit's draw at the same time. If a 20 kWh battery works for a mild‑climate home, plan for 25–30 kWh in a cold region.
Can a heat pump and an EV charger share one solar battery
They can, but not at the same time. Charging an EV pulls 7–11 kW — far more than a heating system. Use a load‑splitting device, or size the solar battery bank for the larger load and charge the EV during the day when solar output is highest.
