Heat Pump Amps and Wattage Calculator
Heat pump capacity is heat moved, not electricity consumed. Enter the rated BTU per hour and efficiency to estimate running amps and watts in heating and cooling mode, plus daily kWh and cost.
Quick answerAt 240 V, 0.95 power factor, COP 3 and EER 12, a 3-ton heat pump is about 15.4 A in heating and 13.2 A in cooling; a 2-ton unit is about 10.3 A and 8.8 A. These are formula estimates—not circuit-sizing values. Use the equipment nameplate MCA and MOCP for electrical work.
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Not for breaker, wire, generator, or transfer-switch sizing.
Not for breaker, wire, generator, or transfer-switch sizing.
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Need broader coverage? Compare plug-in, smart-plug, and whole-home monitorsHow it works
Heating input watts = capacity in BTU/h ÷ (3.412 × COP). Cooling input watts = capacity in BTU/h ÷ EER. Estimated current = watts ÷ (voltage × power factor). Daily kWh = watts ÷ 1,000 × equivalent full-load hours; daily cost = kWh × electricity rate. COP and EER must describe the same operating condition as the capacity for a meaningful estimate.
Heat pump amps and running watts by size
Formula estimates at 240 V, 0.95 power factor, COP 3.0 for heating and EER 12 for cooling—not universal model ratings.
| Capacity | Size | Heating watts | Heating amps | Cooling watts | Cooling amps |
|---|---|---|---|---|---|
| 9,000 BTU/h | 0.75 ton | 879 W | 3.9 A | 750 W | 3.3 A |
| 12,000 BTU/h | 1 ton | 1,172 W | 5.1 A | 1,000 W | 4.4 A |
| 18,000 BTU/h | 1.5 ton | 1,758 W | 7.7 A | 1,500 W | 6.6 A |
| 24,000 BTU/h | 2 ton | 2,345 W | 10.3 A | 2,000 W | 8.8 A |
| 36,000 BTU/h | 3 ton | 3,517 W | 15.4 A | 3,000 W | 13.2 A |
| 48,000 BTU/h | 4 ton | 4,689 W | 20.6 A | 4,000 W | 17.5 A |
| 60,000 BTU/h | 5 ton | 5,861 W | 25.7 A | 5,000 W | 21.9 A |
Actual current changes with outdoor temperature, compressor speed, indoor airflow, defrost, auxiliary heat, and the matched equipment. Do not use this table to choose a breaker, wire, disconnect, generator, or transfer switch; check the nameplate and manufacturer instructions.
Worked 3-ton heat pump example
A 3-ton system has 36,000 BTU/h of nominal capacity. At a heating COP of 3.0, estimated input is 36,000 ÷ (3.412 × 3.0) = 3,517 W. At cooling EER 12, estimated input is 36,000 ÷ 12 = 3,000 W.
At 240 V and an assumed 0.95 power factor, those formula estimates correspond to about 15.43 A in heating and 13.16 A in cooling. Eight equivalent full-load hours would use about 28.14 kWh for heating or 24 kWh for cooling, costing about $4.78 or $4.08 at $0.17/kWh.
Capacity is not electrical wattage
A 36,000 BTU/h heat pump moves heat at a rate equivalent to about 10,551 thermal watts, but it does not normally consume 10,551 electrical watts. COP and EER connect delivered heating or cooling to electrical input. A heat pump can move several units of heat for each unit of electricity.
Do not enter SEER2 or HSPF2 as if they were a single-condition COP or EER. They are seasonal rating metrics. For a closer operating-point estimate, use capacity and efficiency from the same manufacturer performance-table row at the relevant indoor and outdoor temperatures.
Why actual watts change while the unit runs
Variable-speed compressors ramp up and down, and heat-pump capacity and COP change with outdoor temperature. Defrost cycles, crankcase heaters, indoor blowers, pumps, and electric auxiliary heat can add power that a simple capacity-and-COP calculation does not capture. The “equivalent full-load hours” input converts a variable day into a simple energy estimate; it does not mean the compressor literally stays at one wattage for that many hours.
The most reliable operating data come from the manufacturer’s extended performance tables or a properly installed circuit monitor. Utility-bill kWh can validate whole-season use but cannot reveal a specific moment’s running or startup watts.
Do not use this result to size electrical equipment
Breaker, conductor, disconnect, generator, inverter, and transfer-switch sizing require the equipment nameplate and manufacturer instructions, including minimum circuit ampacity, maximum overcurrent protection, locked-rotor or starting characteristics, controls, indoor equipment, and auxiliary heat. The calculated amps above are educational estimates only. Ask a qualified electrician or HVAC professional when sizing or modifying an electrical supply.
Sources used for assumptions: U.S. Department of Energy heat-pump COP calculation procedure; ENERGY STAR current heat-pump criteria and efficiency definitions.
Frequently asked questions
How many amps does a heat pump use?
It depends on capacity, voltage, efficiency, power factor, operating mode, temperature, and compressor speed. At the calculator defaults—240 V, 0.95 power factor, COP 3 and EER 12—a 2-ton formula estimate is about 10.3 A heating or 8.8 A cooling, while a 3-ton estimate is about 15.4 A or 13.2 A.
How many amps does a 2-ton heat pump use?
For 24,000 BTU/h at 240 V and 0.95 power factor, COP 3 gives about 2,345 W or 10.3 A in heating; EER 12 gives 2,000 W or 8.8 A in cooling. The actual nameplate current can differ.
How many amps does a 3-ton heat pump use?
For 36,000 BTU/h at 240 V and 0.95 power factor, COP 3 gives about 3,517 W or 15.4 A in heating; EER 12 gives 3,000 W or 13.2 A in cooling. Auxiliary heat and startup behavior are not included.
Can I size a heat-pump breaker or wire from the calculated amps?
No. Use the equipment nameplate and manufacturer instructions, including minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP). The formula estimate does not include every load, operating condition, startup characteristic, or code requirement.
How many watts does a 3-ton heat pump use?
Using 36,000 BTU/h, COP 3.0 gives about 3,517 W in heating and EER 12 gives 3,000 W in cooling. Real input varies by model, temperature, speed, defrost, blower, and auxiliary heat.
How do I convert heat pump BTU to watts?
For heating, divide BTU/h by 3.412 and then by COP. For cooling with EER, divide BTU/h directly by EER. Match capacity and efficiency at the same operating condition.
Does a heat pump use more watts in cold weather?
It can. Capacity and COP change with outdoor temperature, defrost may operate, and electric auxiliary heat can add a large separate load. Check the model’s cold-weather performance table.
How many kWh does a heat pump use per day?
Multiply average input kilowatts by equivalent operating hours. A 3.517 kW estimate over eight equivalent full-load hours is about 28.14 kWh, before any uncounted auxiliary equipment.
Can I size a generator from this calculator?
No. Generator sizing must cover nameplate running and starting requirements, indoor equipment, controls, pumps, and auxiliary heat. Use manufacturer data and qualified electrical guidance.
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