Usually not — and some batteries provide no backup at all, by design. Three configurations:
- Grid-tied (no backup): replaces the grid at night for maximum savings, zero backup capability. Cheapest, and perfect if outages aren't your concern.
- Partial backup: the most common. Extra equipment backs up 2-10 essential circuits — fridge, lights, wifi. In a blackout, only those run.
- Whole-home backup: multiple batteries, most expensive, everything runs — until the batteries drain, so conservation still matters.
Modern systems "island" during outages: your solar recharges your batteries by day even while the grid is down. But sizing backup honestly — instead of letting a rep imply one battery runs your AC through a week-long outage — is the difference between a happy customer and a furious one.