Backup Power

Backup power refers to the ability of a solar-plus-battery system to continue providing electricity to your home during a utility grid outage. Without battery storage, most grid-tied solar systems automatically shut down during an outage for safety reasons — backup power solves this limitation.

When the grid goes down, a battery system with backup capability detects the outage and automatically disconnects from the grid (a process called islanding). The battery then powers your home’s essential circuits, and if sunlight is available, the solar panels continue generating electricity to recharge the battery. Backup power systems come in two main configurations: critical loads backup (powering only selected essential circuits through a dedicated subpanel) and whole-home backup (powering the entire house, which requires a larger battery system and higher-output inverter). The amount of backup time depends on battery capacity, your energy usage, and solar production. A single 13.5 kWh battery might power essential loads for 12–24 hours, while whole-home backup during heavy usage could drain the same battery in just a few hours. Backup power has become one of the top reasons homeowners add batteries to their solar systems, especially in areas prone to outages.