Air source heat pumps come in various sizes and output capabilities, typically ranging from 9,000 BTU (0.75 tons) to 90,000 BTU (7.5 tons).
The electricity consumption of an air source heat pump can also depend on factors such as size, operating hours, dormant phases, defrost cycles, outdoor and indoor temperatures, and how efficient the heat pump is.
A 12,000 BTU (1 ton) air source heat pump typically uses 3.5 kWh of electricity to warm a 400 sq ft (37.16 sq m) space for an hour. However, the actual electricity consumption of an air source heat pump can depend on the unit’s SEER & HSPF, outdoor temperatures, user’s settings, and a property’s insulation.
Our own air source heat pump is a relatively new model that was installed in our house when it was built in 2017.
As a result, this heat pump is efficient in using electrical energy to transfer heat energy from the outside air into our home and is therefore more efficient on electricity usage.
We discuss in more detail below the electricity usage of our air source heat pump, as well as explaining how an air source heat pump’s electricity consumption can depend on factors such as its technology, age & condition, compatibility in a specific climate and for a particular property, and how you use it.
Two air source heat pumps of the same brand with identical specifications can have different electricity consumption because of a range of external factors that can affect every heat pump installation.
It’s therefore hard to provide a precise energy consumption unit for any such appliance without seeing it in use in the real world.
Furthermore, air source heat pumps can have a different SEER (Seasonal Energy Efficiency Rating) and HSPF (Heating Seasonal Performance Ratio).
Generally, an air source heat pump’s electricity consumption is inversely proportional to its SEER and HSPF.
The following table has the typical electricity usage for standard air source heat pump sizes:
|Air Source Heat Pump Size||Heated Area / Space*||Electricity Usage|
|9,000 BTU (0.75 tons)||300 sq ft (27.87 sq m)||2.6 kWh|
|12,000 BTU (1 ton)||400 sq ft (37.16 sq m)||3.5 kWh|
|15,000 BTU (1.25 tons)||500 sq ft (46.45 sq m)||4.4 kWh|
|18,000 BTU (1.5 tons)||600 sq ft (55.74 sq m)||5.3 kWh|
|20,000 BTU (1.66 tons)||666 sq ft (61.87 sq m)||5.8 kWh|
|22,500 BTU (1.87 tons)||750 sq ft (69.67 sq m)||6.6 kWh|
|25,000 BTU (2 tons)||833 sq ft (77.38 sq m)||7.3 kWh|
|30,000 BTU (2.5 tons)||1,000 sq ft (92.9 sq m)||8.8 kWh|
|45,000 BTU (3.75 tons)||1,500 sq ft (139.35 sq m)||13.2 kWh|
|60,000 BTU (5 tons)||2,000 sq ft (185.80 sq m)||17.6 kWh|
|75,000 BTU (6.25 tons)||2,500 sq ft (232.25 sq m)||22 kWh|
|90,000 BTU (7.5 tons)||3,000 sq ft (278.70 sq m)||26.3 kWh|
*Maximum area or space during mild winters. Reduce the coverage by ~30% for colder climates and by ~50% for extreme winters with prolonged sub-freezing conditions.
Choose the relevant kWh from the table per the capacity of your air source heat pump. Multiply the kWh with the number of hours you will operate the unit every day and night or throughout the winter. You will have a fair estimate of the electricity usage of your air source heat pump.
Air Source Heat Pump Electricity Consumption Example
Our Mitsubishi Electric air source heat pump extracts heat energy from the outside air for use in both our home’s central heating and domestic hot water.
It has a heating capacity range of 3.4-11.2kW (11,600-38,200 BTUs), with a Coefficient of Performance (COP) of 3.34 to 4.47, meaning that it can generate over 3 units of heat energy for every unit of electrical energy consumed.
The higher the COP of an air source heat, the less electricity can be used to heat your home to the same temperature (if all other factors remain the same).
The data plate on our air source heat pump details the information for this specific model.
Our heat pump also has a power input of 2.51 to 3.35kW in heating mode (we don’t use it for cooling).
In terms of our electricity bill, we spend just over £200 (£260) per month on average for our 5-bedroom house, and we have no other energy bills.
A large amount of this cost will be from our air source heat pump operating. As we use our heat pump for both heating and hot water, hot water demand should stay relatively the same throughout the year, but the electricity usage will increase through the colder months as heating demand increases.
Various internal and external factors influence the electricity usage of all air source heat pumps, irrespective of brand, model, capacity, and type.
However, the type and capacity are also key elements, especially if incompatible with your property or specific needs.
The following three sets of factors have quintessential roles in influencing electricity usage and your expenditure.
Air to air source heat pumps are generally ducted or ductless. Both have their advantages depending on the type of property you have and how much space you want the appliance to heat. However, the capacity is of immense consequence as you cannot opt for an undersized or oversized unit.
See our article comparing ductless and ducted air source heat pumps for more information.
An undersized unit is inefficient and ineffective, and your energy consumption will be higher.
However, an oversized unit is also inappropriate because it will frequently switch off and on when it attains the user-selected temperature. Frequent reboots can lead to inefficiency. Also, the air source heat pump’s longevity can reduce drastically due to the restarts.
Our air source heat pump was sized appropriately to the size of our 5-bedroom house. As a result, it consumes the average amount of electricity that the manufacturer specified.
Had this unit been undersized or oversized then it could be working too hard or being underutilized, which could lead to increased electricity usage.
Air source heat pumps with a minimum of 14 SEER and 8.5 HSPF ratings are reliably efficient.
SEER (seasonal energy efficiency rating) is the cooling efficiency of a heat pump.
HSPF (heating seasonal performance ratio) is the heating efficiency of a heat pump.
Heat pumps can also be used for cooling if desired. We have an article covering heat pump cooling in more detail here.
COP (coefficient of performance) is another way in which efficiency of a heat pump is expressed but is measured at specific temperatures rather than seasonal varying temperatures.
The coefficient of performance (COP) is the net outcome of an air source heat pump’s Seasonal Energy Efficiency Rating (SEER) and Heating Seasonal Performance Ratio (HSPF). SEER and HSPF are correlated, and if both are high, your air source heat pump will have greater COP.
Essentially, the COP is the proportion of output per the quantum of energy used by appliances like an air source heat pump. HVACs, refrigerators or freezers, and many other appliances have a COP, too. A COP of 1 means an appliance’s output is equivalent to the energy used.
Air source heat pumps have COPs ranging from 2 to 4. Anything less than 2 won’t adhere to the electricity usage patterns cited in this article, irrespective of the climate zone, size, and area you have to heat during winters. Also, your settings and usage can influence the COP in reality.
The efficiency of our heat pump is expressed using a COP for both heating (COP) and cooling (EER COP)
Whatever way in which the efficiency of an air source heat pump is expressed, the higher the number, the less electricity the unit will consume.
An 18 SEER air source heat pumps usually have a high HSPF rating. Air source heat pumps are rated as high as 20.5 SEER.
Both SEER and HSPF indicate Coefficient of Performance (COP) or efficiency in normal jargon.
Modern air source heat pumps, especially those for cold climates, have a COP of more than 3. You will find models with COP as high as 4. Anything between 3 and 4 will use less electricity.
Cold climate air source heat pumps with a coefficient of performance greater than 3.5 use less electricity than standard units with an efficiency of around 2 in freezing winters.
Regular air source heat pumps are inefficient when temperatures hover at 32°F (0°C) and dip further.
The efficiency aside, your selected settings for indoor temperatures and the unit’s smart features, if available, will influence the actual electricity usage.
Don’t select high or very warm indoor temperatures as the unit will keep running and consuming electricity. Also, avoid changing the indoor temperature setting frequently as a stressed unit will use more energy.
5 Tips To Reduce Air Source Heat Pump Electricity Usage
Like all appliances consuming significant electricity, an air source heat pump will require much more energy when it’s stressed.
Older heat pumps with lower tonnage and failing components or unsuitable models for the climate zone will spike your electricity usage and hence expense.
Here are 5 tips to reduce air source heat pump electricity usage:
- Choose an air source heat pump of optimum capacity (BTU/kW/tons) per your needs.
- Try to opt for higher SEER & HSPF and thus a more effective 3 to 4 COP.
- Avoid unusually high heat settings when the outdoor temperatures are too cold.
- Review the insulation in your house, including any weatherstripping you may have.
- Consider timely preventive maintenance to increase efficiency and prevent malfunctions.
Moderate heat settings for optimum periods will contain the electricity usage within expected thresholds. Frequent starts, shutdowns, defrost cycles, and higher temperatures to heat a room quickly will increase the electricity usage of an air source heat pump.
Expect a typically air source heat pump to use up to around 3.5kW of electricity per hour.
However, the actual real world electricity usage for an air source heat pump will be dictated by a number of factors such as the efficiency rating of the unit, how old it is and how well it has been maintained, the current outside temperatures, the desired internal temperatures, and how well the heat pump works with the internal heating components.