A backup power system is a normally grid-connected battery power system designed to interact with the grid and keep your home operational during grid power outages. It is similar to an off-grid system but differs in a few ways. Backup power systems may be smaller and aren't necessarily designed to provide for complete energy needs like a system that's designed to be permanently off-grid. Backup systems also have user options to effectively eliminate grid demand charges using time-based operation.
Backup systems typically offer at least 24 hours of power under normal conditions, but the actual duration depends on the system size, month/season, weather, home/appliance efficiency, and the time of day that energy is used most. With careful energy management, a small system can usually keep essential appliances running indefinitely as long as solar energy is available. Larger systems can cover all energy needs most of the time by effectively zeroing grid power usage.
Backup power systems are typically configured in one of two ways:
Whole-House Backup (most common): This configuration backs up the entire home.
Partial Backup: This option is used when it is necessary to separate essential loads, such as refrigeration, lighting, and power outlets, from non-essential loads or loads that consume excessive power, such as electric heating, electric clothes dryers, and electric saunas, that will not be backed-up. An additional breaker panel to separate the loads is required in this case.
In addition to providing backup power, battery power systems offer additional features such as:
Storing extra solar energy from the daytime for use overnight
Reducing demand from the grid
Reserving energy for use during peak times
Tesla Whole-Home Backup with Powerwall 3:
