How Many Watts Does a Heat Pump Use? Nameplate, kWh and Backup
By Seamless Home Team, Home services operations · November 5, 2026 · Updated November 5, 2026
Quick answer
A heat pump's running watts are on the outdoor unit's nameplate — look for rated load amps (RLA) or a wattage figure, then multiply amps by volts. As approximate planning numbers, Otter Tail Power Company's appliance chart lists about 2,000 watts for a 2.5-ton, 15 SEER air-source heat pump and about 3,700 watts for a 3-ton cold-climate unit (8.1 HSPF2) operating down to 0°F. Actual draw rises in extreme weather and when electric strip heat or a backup furnace kicks on. For energy, watts × hours ÷ 1,000 = kWh.
A heat pump moves heat rather than making it with a big resistance element, so its electric draw is usually lower than an electric furnace for the same heating job. It is still one of the largest continuous loads in many homes — especially in cold weather, when backup heat may switch on.
Approximate wattage (planning numbers)
Otter Tail Power Company publishes an appliance energy-use chart with approximate wattages for common heating and cooling equipment. Two heat-pump rows on that chart:
| Equipment (Otter Tail chart) | Approx. wattage |
|---|---|
| Air-source heat pump, 15 SEER, 2.5 tons | 2,000 W |
| Cold-climate heat pump, 3-ton, 8.1 HSPF2 (operating to 0°F) | 3,700 W |
Those are planning figures for the utility's examples, not a promise for your outdoor unit. Capacity (tons), efficiency (SEER2 / HSPF2), outdoor temperature, fan speed and whether strip heat is on all change the real number.
Read the nameplate first
The figure that applies to your house is on the outdoor unit:
- Find the data plate on the condenser.
- Note the voltage (often 230 V or 240 V single-phase).
- Prefer rated load amps (RLA) or a listed wattage for running power.
- Note minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP) for breaker and wire sizing — those are installation limits, not continuous running watts.
Running watts ≈ RLA × volts. Example: 12 A × 240 V ≈ 2,880 W while the compressor and fan are in that rated condition.
Amps and kWh
- Amps = watts ÷ volts. At 240 V, 2,000 W ≈ 8.3 A; 3,700 W ≈ 15.4 A.
- kWh = watts × hours ÷ 1,000. A 2,000 W unit running 8 hours uses about 16 kWh that day.
Cost is kWh × your rate. As an illustration only, 16 kWh at 16¢/kWh is about $2.56 for that day. Your bill shows the rate that applies at your meter — including time-of-use peaks if you are on one.
Why cold weather changes the answer
Air-source heat pumps lose capacity as outdoor air gets colder. Many systems then:
- Run the compressor longer or at higher power, and/or
- Turn on electric resistance strip heat (often several kilowatts), or
- Switch to a gas furnace in a dual-fuel setup (electric draw drops to the furnace controls and blower).
That is why a summer cooling wattage and a January heating wattage for the same outdoor unit can look very different on a meter.
Heat pumps and home batteries
Heating and cooling are among the hardest loads to back up. A battery can sometimes carry a heat pump briefly if the system is efficient, the battery is large, and only that HVAC circuit plus a few essentials are on the critical load panel. Many designs leave the heat pump off the panel and keep lights, refrigeration, internet and medical devices instead — or keep only the furnace controls when the heat source is gas.
We do not quote a runtime until someone sees the panel and the nameplate.
Related loads
- How many watts a furnace uses — fan and ignition when the heat source is gas or oil.
- How many watts a house uses — where HVAC sits in the whole-home picture.
- How many watts a space heater uses — portable resistance heat as a small backup circuit.
- HVAC for homeowners — replacement treated as a designed job, not a like-for-like swap.
Startup surge vs running watts
Compressors draw a short spike of current when they start (locked-rotor amps on some plates). That spike lasts seconds, not hours. Battery and inverter sizing care about both the continuous running watts and whether the inverter can absorb that brief surge. Nameplate LRA or "max fuse" figures are not the same as continuous running watts — use them for equipment compatibility checks, not for estimating monthly kWh.
Separating the outdoor unit from indoor fans
A split heat pump has an outdoor condenser/compressor and an indoor air handler or furnace blower. The outdoor nameplate covers the compressor and outdoor fan. The indoor blower has its own motor watts, often listed on the air-handler or furnace label. Whole-home draw while heating or cooling is outdoor running watts plus indoor blower (and any electric strip heat). If you only read the outdoor plate, you undercount the circuit the house is actually using.
Using a meter instead of a chart
A plug-in meter works for a window or portable unit on a receptacle. For a hard-wired split system, a clamp meter on the outdoor disconnect (by a qualified electrician) or a whole-home energy monitor with a labeled circuit is the practical path. Compare a few heating and cooling hours to the Otter Tail planning numbers — they should be in the same ballpark for a similar tonnage, but your house will not match the chart exactly.
What this means for a Seamless quote
When we quote heat pump work or a battery critical-load panel, we start from your equipment labels and panel schedule, not from a website average. The Otter Tail figures are here so you can sanity-check a label and understand order of magnitude before a site visit.
Sources
- Otter Tail Power Company, Appliance energy use charts (approximate wattages and seasonal kWh examples; rates on that page are Otter Tail's own illustrations).
- Your outdoor unit nameplate for RLA, MCA, MOCP and voltage — the controlling document for one house.
Frequently asked questions
How many watts does a heat pump use?
It depends on the unit and the outdoor temperature. Otter Tail Power Company's appliance energy-use chart lists about 2,000 watts for a 2.5-ton, 15 SEER air-source heat pump and about 3,700 watts for a 3-ton cold-climate heat pump. Your outdoor unit's nameplate is the figure that applies to your house.
How do I find my heat pump's wattage?
Read the nameplate on the outdoor condenser. It usually lists rated load amps (RLA) or minimum circuit ampacity (MCA) at a voltage such as 230 V or 240 V. Watts ≈ amps × volts. MCA is a circuit-sizing number, not continuous running watts, so prefer RLA or a listed wattage when both appear.
How many amps does a heat pump use?
Amps = watts ÷ volts. At 240 V, a 2,000-watt running load is about 8.3 A; a 3,700-watt load is about 15.4 A. Startup (locked-rotor) current is higher for a short moment. The breaker is sized from the nameplate MCA and maximum overcurrent protection (MOCP), not from a website average.
How many kWh does a heat pump use?
Watts × hours ÷ 1,000. A 2,000-watt unit running 8 hours uses about 16 kWh that day. Seasonal totals vary with climate, thermostat setpoints and whether backup heat runs. Otter Tail's chart shows example seasonal kWh for its listed models; your bill and a plug-in or whole-home meter are more accurate for one house.
Does a heat pump use more power when it is cold outside?
Usually yes. As outdoor temperature drops, an air-source heat pump has to work harder, and many systems add electric resistance strip heat or switch to a gas furnace. That backup heat can draw several kilowatts by itself, which is why winter peaks matter for bills and for battery sizing.
Can a home battery run a heat pump in an outage?
Sometimes for short periods if the heat pump is on the critical load panel and the battery is large enough — but heating is one of the heaviest residential loads. Many backup designs leave the heat pump off the panel and keep only controls, a small space heater circuit, or a gas furnace's ignition and blower. We size that from the panel, not from a generic wattage.