When the grid goes down, a home backup battery keeps your essentials running: the fridge, the internet, medical devices, and a few lights. Unlike a gas generator, it is silent, works indoors, and needs no fuel runs at 2 a.m.
There are two broad paths, and picking the right one saves you thousands.
1. Plug-in vs whole-home
- Plug-in / expandable stations: large portable units (often 2 to 6 kWh, expandable) that you plug into with extension cords or a small transfer switch. Cheaper, renter-friendly, no electrician required for the basic setup.
- Whole-home systems: permanently installed batteries wired to your panel through an automatic transfer switch. They power the whole house and switch over instantly, but need a licensed installer.
2. Sizing: how many kWh do you need?
Add up what you truly need to keep running during an outage, then multiply by the hours you want to cover. Most households want the fridge, internet, phone charging, and a few lights, which a 2 to 5 kWh battery covers for a day or more.
Use the runtime calculator to see how long a given battery lasts with your appliances.
Runtime calculator
Cycling appliance: it only draws power about 33 % of the time (the motor stops once it reaches temperature).
Estimated runtime
≈ 2d 4h
Estimate for 2000 Wh usable at ~85 % (inverter losses + real depth of discharge). Real numbers vary with temperature, battery age, and appliance efficiency.
3. Add solar to recharge off-grid
Pairing your backup battery with solar panels lets it recharge during a multi-day outage, so you are not stuck when the battery runs flat. This is where backup crosses over into a small home solar setup.
