A typical 3-ton whole-home heat pump uses about 3,500 watts while running, roughly 2,000-6,000 W by size, on 240 volts. Auxiliary electric heat strips add another 5,000-15,000 watts when they switch on.
- Running watts
- 3,500 WTypical; 2,000–6,000 W across models
- Starting watts
- 7,000 WEstimate for a single-stage ~3-ton unit; Generac says a 3-ton…
- Per day
- 33.6 kWh24 h of use, cycling
- Current
- 14.6 AAt 240 V while running
Figures checked against DOE, ENERGY STAR and manufacturer data on . Your model's label is the final word.
Watts by model and setting
Most heat pump models draw between 2,000 and 6,000 W while running; a typical one draws about 3,500 W. Assumes a 3-ton heat pump (compressor, outdoor fan and indoor blower) at about 3,500 W running 40% of a cold day, with no auxiliary heat; each hour of 10 kW aux heat adds 10 kWh.
- Capacity in tons and outdoor temperature: heating output and efficiency drop as it gets colder
- Auxiliary (backup) resistance heat strips, commonly 5, 10 or 15 kW, engage in cold weather or defrost and dominate electric use
- Efficiency ratings (SEER2 for cooling, HSPF2 for heating) and whether the compressor is single-stage or variable-speed
- Thermostat setbacks that trigger aux heat during recovery
- Duct leakage and home insulation
Running a heat pump on backup power
This is a 240 V appliance. It needs a generator with a 240 V outlet or a transfer switch or interlock installed by a licensed electrician; most portable power stations only supply 120 V.
- Size a generator for the heat pump with auxiliary heat locked out; strips of 10 kW or more can overload most standby generators
- A 240 V heat pump needs a properly installed transfer switch or interlock; never backfeed through an outlet
- Variable-speed (inverter) heat pumps have low starting surge and are much easier on generators than single-stage units
- Standby generators must be outdoors with clearances per the manufacturer to prevent carbon monoxide entering the home
Add it to the generator calculator
Questions people ask
What is auxiliary heat on a heat pump?
It is electric resistance heating, usually 5-15 kW of heat strips in the air handler, that supplements the heat pump in very cold weather or during defrost. It uses two to three times more electricity per unit of heat than the heat pump itself.
Can a generator run my heat pump?
A whole-home standby generator usually can run the heat pump itself, but plan to disable or load-manage the auxiliary heat strips, which can draw 10,000 W or more.
How much more efficient is a heat pump than electric heat?
ENERGY STAR says an air-source heat pump can deliver up to three times more heat energy than the electricity it uses, while resistance heat delivers about one to one.