How Long Will a Home Battery Run During an Outage?
It depends on your loads, battery size, and whether solar is recharging it. Here's a realistic way to think about backup runtime — and why AC is the hard part.
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Short answer: There's no single number. A typical home battery can keep essentials — fridge, lights, internet — running for many hours to a day or more, but air conditioning drains it far faster. Actual runtime depends on battery capacity and charge, your loads, weather, solar production, and equipment startup surges. No home battery powers a whole house indefinitely.
The honest variables
- Battery capacity and how full it is when the outage starts
- Which loads you're running (essentials vs. AC and pumps)
- Whether solar is recharging the battery during the day
- Startup surges from motors like AC compressors and well pumps
- How long the outage lasts and what the weather is doing
Why AC is the hard part
Central air conditioning draws far more than everything else combined. Running it on battery alone usually needs a larger system, and in a multi-day outage you'll want daytime solar to recharge — which is exactly when storm clouds cut production. It's doable, but it has to be designed for honestly, not promised casually.
Pairing a battery with solar can extend backup by recharging during the day. But production varies, especially during storms — so we plan for realistic conditions, not best-case.
Questions worth asking
- Which specific circuits will be backed up?
- How long will my essentials run with no solar recharging?
- What would it take to run my AC, realistically?
• When this might not make sense
We'd rather lose a sale than put you in the wrong solution. Reasons we might tell you to wait or pass:
- —Expecting to run central AC indefinitely on a single small battery
- —A proposal promising 'unlimited' or 'off-grid forever' backup
- —No plan for how the battery recharges during a multi-day outage
Sources
- Enphase home battery systems — EnphaseSecondary
- Tesla Powerwall — TeslaSecondary
Design an honest backup plan
Tell us what you need to keep running and we'll size a realistic option — no 'off-grid forever' promises.