Can BTM storage provide backup power during outages?

Yes, but it requires intentional design. A standard grid-tied BTM system optimized purely for bill savings won't automatically provide backup power — it needs additional hardware (a transfer switch or microgrid controller) and software configuration to island from the grid during an outage.

When configured for backup, the system detects a grid outage, disconnects from the utility, and powers designated critical loads from the battery. Which loads get backed up and for how long depends on the battery's capacity and the building's energy needs. Most commercial systems prioritize critical circuits — lighting, refrigeration, IT, security — rather than trying to back up the entire building.

There's a trade-off here: reserving battery capacity for backup means that capacity isn't available for daily bill savings. If you hold 30% of the battery in reserve for emergencies, your demand charge savings drop accordingly. Some operators accept this trade-off for the resilience value; others let the battery fully cycle for savings and accept that outage coverage will depend on state of charge at the time.

Pairing storage with solar significantly extends backup duration. On a sunny day, the solar array recharges the battery, potentially providing days of backup for critical loads rather than just a few hours. This solar-plus-storage configuration has become the standard approach for facilities where continuity of operations is a priority.