How Long Can a Solar Battery Power Your Home?
A battery lets you use solar power after sunset and keeps essentials running during brownouts. How long it lasts depends on its capacity and what you're powering at the time.
It's about kWh, not just kW
Battery capacity is measured in kilowatt-hours (kWh) — the total energy it can store. A 10 kWh battery holds 10 kWh of usable energy (a little less, since you rarely drain to zero).
How long that lasts depends on your load. Running 1 kW of appliances, a 10 kWh battery lasts about 10 hours. Running 2 kW, about 5 hours. It's simple division: capacity ÷ load = hours.
What you choose to back up
Most homeowners don't try to run everything on battery. Instead they back up essentials — lights, fans, fridge, internet, phone charging, maybe one aircon. That stretches backup time dramatically.
Air conditioning and electric water heaters are the biggest loads. If you want to run aircon overnight on battery, you'll need a larger bank; for essentials-only, a modest battery goes a long way.
Sizing your backup
- Essentials only (~0.5 kW): a 5 kWh battery ≈ 10 hours.
- Essentials + 1 aircon (~1.5 kW): a 10 kWh battery ≈ 6–7 hours.
- Whole-home overnight: usually needs 15 kWh+ and careful design.
Backup time is capacity divided by load. For most homes, a 5–10 kWh battery covers essentials through the night or a typical brownout. We size the battery to the hours of autonomy you actually want.
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