What Is an Automatic Backup Generator?

An automatic backup generator is an electrical generator that is permanently wired to a home's electrical system and automatically provides backup power to important circuits in the event of an electrical outage. Automatic backup generators usually run on natural gas or liquid propane.

An automatic backup generator connects to a home electrical system through a transfer switch, which connects the generator to a portion of the electric panel. It supplies power to those circuits that are connected to the transfer switch within a minute of detecting a loss of grid power. Generally, the switch to backup power occurs less than a minute after grid power goes down.

Homeowners must choose the appropriate circuits to connect to the backup generator by deciding what equipment is important enough to run off generator power temporarily and by determining which circuits connect to that equipment. Important equipment to power may include the refrigerator, well pump, security system, air conditioning and medical equipment.

Automatic backup generators use natural gas or propane as a fuel source. While portable generators require constant refilling with gasoline or diesel, an automatic backup generator tied to a large household propane tank or municipal gas line can run indefinitely, offering peace of mind. When grid power returns, an automatic backup generator switches the home's power source back to the grid and shuts down.