A heat pump uses 1,000 to 4,600 watts when running.
Heat pump wattage is based mainly on size and energy efficiency.
Read on for heat pump wattage by size and to learn the right generator size for a heat pump.
Heat Pump Wattage
How much electricity does a heat pump use?
Size is the most significant factor in how many watts a heat pump uses. Within each size, efficiency is also important. These are running watts.
1.5 – 5 Ton Heat Pump Wattage
| Heat Pump Size | Heat Pump Wattage |
| 1.5 ton | 1000 – 1400 watts |
| 2 ton | 1600 – 1800 watts |
| 2.5 ton | 2200 – 2600 watts |
| 3 ton | 2500 – 2900 watts |
| 3.5 ton | 3200 – 3500 watts |
| 4 ton | 3500 – 3800 watts |
| 5 ton | 4000 – 4600 watts |
Note: This is the average total wattage of the air handler and outdoor unit. This table is based on 95F outdoor design temp. The air flow is based on 400 CFM per ton.
Why is there a range for each size? Because today’s standard split system heat pumps are 14 SEER to 26 SEER in efficiency. Every year the maximum SEER rating goes up; heat pumps are more efficient than ever and only getting better at saving energy.
For an example showing how efficiency affects watts used, consider a 3 ton heat pump.
How Many Watts Does a 3 Ton Heat Pump Use
| SEER Rating – Higher is More Efficient | Average Watts Used |
| 14 SEER | 3050 watts |
| 16 SEER | 2815 watts |
| 18 SEER | 2630 watts |
| 20 SEER | 2500 watts |
| 22-26 SEER | 2325 – 2415 watts |
The higher the SEER rating, the more efficiently the unit turns electrical energy into effective air conditioning.
How Many Watts Do Heat Pumps Use with Heat Strips?
Some sites state that heat pump wattage is closer to 15,000 watts or more.
But that wattage might only be accurate when the unit is in heating mode. If the air handler contains auxiliary heating strips or coils and their wattage is factored in, then that high wattage estimate might be correct.
Air handler internal heaters range in watts from 5kW to 20kW. Their purpose is to provide extra heat when the heat pump can’t keep up in extreme cold weather and to give you emergency heat when the heat pump isn’t working.
Starting Watts vs Running Watts
Have you heard your heat pump make a sharp, quick electrical buzz when running? That’s a surge of electricity, enough wattage to get the compressor started and the refrigerant flowing.
Starting watts are also called surge watts. They are two to three times higher than running watts and should be considered when choosing a generator size for a heat pump. If the generator doesn’t have enough juice to start the compressor, it is too small.
What Size Generator Do I Need to Run a Heat Pump?
These generator sizes cover heat pump starting watts, which are approx. 3 times running watts.
What Size Generator Do I Need To Run A Heat Pump
| Heat Pump Size | Minimum Generator Size |
| 1.5 ton | 2800 watts |
| 2 ton | 3600 watts |
| 2.5 ton | 5400 watts |
| 3 ton | 6000 watts |
| 3.5 ton | 7000 watts |
| 4 ton | 7600 watts |
| 5 ton | 8500 watts |
Note that generator sizes in the chart do not consider auxiliary heating coils or strips installed in the air handler and backup or make-up heat.
Will a 20kW generator run a heat pump?
Yes, a 20kW will run a heat pump. 20kW is 20,000 watts, and even the largest heat pump doesn’t need that many watts to start.
What size generator for a 3 ton heat pump?
A 7000 watt generator is enough to power a 3 ton heat pump. That’s the minimum size you should purchase.
But if you plan to run other electrical appliances, lights and equipment off the same generator, you’ll have to choose a larger size. You won’t want to have to pick and choose what essentials get power.
Will a portable generator run a heat pump?
Yes – possibly. Larger portable generators in the 5000-watt range and above can likely handle the needs of a heat pump.
However, most homeowners choose a standby or whole-house generator that is hardwired into the home’s electrical panel.
Does Outside Temperature Affect Heat Pump Wattage and Power Consumption?
Yes, outside Temperature, aka ambient temperature, affects heat pump wattage. As the temperature rises from 75F to 95F, most heat pumps will become less efficient and use between 10% and 14% more energy.
Once temperature rises above 100F, the unit will use another 8% to 10% more power.
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Final Note: This page is about standard air source heat pumps. Mini split heat pumps and geothermal heat pumps have different requirements for starting and running watts. They are generally more efficient, and so they use less energy.
