Home backup batteries: how they connect

Essential loads vs whole home

Backing up a refrigerator, lights, internet and a furnace fan takes much less battery than running central air or an electric range. Most designs start with a critical-loads list.

Transfer equipment

During an outage the home must be isolated from the grid so power cannot flow back onto utility lines, which endangers line workers. That is the job of a transfer switch, interlock or battery gateway.

With or without solar

A battery alone can cover short outages and, where utility rates allow, shift usage away from peak hours. With solar, it can recharge during a longer outage if the system is designed to operate off-grid.

Permits and incentives

Local codes, utility interconnection rules and incentive programs vary and change. Check your local building department, your utility and IRS.gov for current federal tax rules before planning around a credit.

FAQ

Where do I go next?

Try the power planner to put numbers to your own situation, or see the product picks on the deals page.

Terms used here

Transfer switch

Device that isolates home circuits from the grid during backup.