Battery banks in a home serve the same purpose as a traditional generator that runs on diesel, gasoline, propane, or natural gas. Unlike a traditional generator, a battery backup system does not require you to buy and store fuel or rely on fuel delivery during an outage. When paired with a solar array, the battery will be charged with the solar electricity you produce. If you do not pair your batteries with solar, the battery will charge and recharge only from utility-supplied grid electricity. This limits its usefulness for backup power purposes during a utility outage as it will only be able to discharge once before needing the utility grid to be restored for it to recharge.
Powering your entire home with a battery system can get expensive. This is why many homeowners install a smaller battery bank to power select “critical loads”, such as medical equipment or a refrigerator, in their home during the event of a grid outage. If you feel strongly about powering your entire home during an outage, a whole-house fossil fuel-powered generator may be more cost effective.