A home with a heat pump requires a minimum 22kW Generac generator for whole-house coverage because heat pumps draw significantly more electrical current than gas furnaces, especially during the electric resistance backup heating that activates when outdoor temperatures fall below the heat pump efficiency threshold. A 3-ton heat pump in heating mode draws approximately 3,500 to 5,000 running watts plus a starting surge of 8,000 to 12,000 watts. A gas furnace blower draws only 300 to 800 watts with a modest starting surge.
The critical sizing scenario for heat pump homes occurs in very cold weather when the heat pump activates electric strip heating as a backup. Electric strip heaters typically draw 5,000 to 15,000 watts depending on the capacity installed, which can push total home demand well above what a 14kW or 18kW generator can supply. A 22kW generator handles a 3-ton to 4-ton heat pump with up to 10kW of electric strip backup alongside standard household loads. A 24kW or 26kW generator is appropriate for 4-ton to 5-ton heat pumps or homes with larger strip heat banks.
All-electric homes with heat pumps and no gas appliances represent the highest demand scenario and consistently require 24kW or larger. The Generac 24kW Guardian (7261) is a common choice for these homes. Browse our full Generac home standby generator collection or contact our licensed master electrician team for a heat pump load calculation. Free Freight Insurance Included.