How many kWh of battery do I need to back up my house?

Start with what you want to back up

Battery sizing has one honest answer: it depends on what you want to run, and for how long. There's a big difference between keeping the essentials alive through a short outage and running your entire air-conditioned house for three days. Pick your goal first, and the capacity follows.

Two numbers describe a battery. Capacity (kWh) is how much energy it holds, which sets how long it lasts. Power (kW) is how much it can push out at once, which sets how many things you can run at the same time. You need enough of both.

Essentials-only backup: about 10 to 20 kWh

If your goal is to ride out the common outage, refrigerator, lights, WiFi, phone charging, a few outlets, and maybe the furnace fan, that's a modest draw. Those loads together often sit around 10 to 20 kWh per day, so a battery in that range can carry a home through most overnight and multi-hour outages comfortably.

Whole-home backup, including AC: about 30 to 60 kWh

The moment you add central air conditioning, the math jumps. AC is the single biggest load in most homes, drawing roughly 3 to 5 kW whenever it's running, and in a Texas summer it runs a lot. Add an electric water heater, an EV charger, or a pool pump and you're firmly in whole-home territory. To keep all of that running through a real outage, most homes want 30 to 60 kWh of usable storage.

How to read your own electric bill

You don't have to guess. Grab your utility bill and find the total kWh used for the month, then divide by 30. That's your average daily usage. A home at 900 kWh/month is using about 30 kWh a day; a big all-electric home at 1,500 kWh/month is closer to 50 kWh a day. Match your battery to the slice of that you actually want backed up, and how many days of runtime you want if the sun isn't out.

One thing that quietly extends your runtime: solar. During a daytime outage, your panels recharge the battery, so a paired solar + battery system can stretch a sunny multi-day outage far longer than the raw kWh number suggests. (That's also why solar alone shuts off in a blackout but works with a battery.)

What SOLRITE installs

Rather than make you do the math, SOLRITE sizes the system for you off your last 12 months of usage. In Texas, that's a 60 kWh sonnen system (three 20 kWh modules), enough for serious whole-home coverage. In California and Illinois, a Duracell Max Hybridsystem scales from about 20 kWh up to 60 kWh depending on your home. And because it's a $0-upfront VPA, right-sizing up for AC and EVs doesn't hit you with a bigger bill, the equipment cost isn't yours.

Wondering whether it's worth it at all? Start with are home batteries worth it in 2026.