Air source heat pumps can help to regulate a building’s heating and cooling more efficiently and can be more sustainable than other conventional forms of heating such as furnaces or boilers.
Gas boilers are electric but require a supply of gas in order to work. Air source heat pumps don’t burn any such fuel to produce heat and so are air source heat pumps purely electric?
Air source heat pumps are electrical appliances and only require an electrical supply in order to work. They function much like refrigerators in reverse and use electricity to run fans and a compressor.
Our air source heat pump is connected to the mains power supply for the house.
We explain more about air source heat pumps as solely electrical appliances in more detail below using our own heat pump as an example.
How Is An Air Source Heat Pump Powered?
Air source heat pumps are electrical appliances and are powered by electricity only. Unlike more conventional heating such systems such as oil or gas-based units, air source heat pumps only require a mains electrical supply to work and generate heat.
When an air source heat pump (ASHP) is installed outside, it will need to be connected to the mains electricity for the property.
For example, our air source heat pump is installed on the side of the house and a power cable from inside the garage behind the wall provides the electricity supply needed to power all the functions on the external heat pump unit.
Our heat pump has an isolator switch for the electrical supply as it meets the external wall where the power cable is run from inside the garage.
There’s no other form of power to our heat pump. The only other apparatus connected to the unit is the two pipes connected to the back that serve as the inlet and outlet routes for the refrigerant.
When the electricity used to power an air source heat pump comes from renewable sources itself, such as from solar panels, an ASHP can be considered to be a very environmentally friendly and sustainable way to heat a home.
Do Air Source Heat Pumps Use Electricity?
Air source heat pumps only use electricity to operate.
An air source heat pump converts this electrical energy into heat energy.
The efficiency of an ASHP’s to convert this electricity into heat can be measured in terms of the Coefficient of Performance (COP).
For example, our heat pump has a minimum COP of 3.34 as stated on the information plate for the unit, meaning that it will produce over 3 units of heat energy for every 1 unit of electricity consumed.
The greater the coefficient of performance, the more heat can be produced for your home from electricity.
See our article on air source heat pump COP for more information.
Air source heat pumps can use less electricity with greater performance in milder climates compared to other electrical systems.
They can also cost less for more heating and cooling compared to traditional gas or oil systems.
If you were already using gas for heat, air source heat pumps can make your electric bill increase, but this cost increase can be offset with reduced energy bills elsewhere. When people install heat pumps, their costs and savings can shift depending on their current setup.
Another difference between air source heat pumps and other forms of heating like furnaces and boilers is the ignition.
Heat pumps don’t ignite. They run on the same engineering as refrigerators except that they move hot and cold air between the inside and outside of a home. The heat brought in heats the coils, and those let the heat into the house.
The aim of an air source heat pump is to produce as many units of heat as possible per unit of electricity (the highest COP possible).
Air source heat pumps work best with proper installation and in mild climates. In these conditions, these heat pumps can typically provide three times more energy as heat than the electric costs needed to transfer heat.
An ASHP achieves this by transferring heat rather than having to convert it. For comparison, combustion appliances work by converting energy forms.
Colder regions with frequent subfreezing temperatures can make heat pumps work less efficiently since there’s less heat in the outside temperature to extract.
However, air source heat pumps can still work very effectively even down to around -25°C (-4°F) or more because the boiling point of the refrigerant used is very low.
See our article on air source heat pump efficiency for more information.
Issues Affecting Air Source Heat Pump Electrical Efficiency
Several factors can cause issues with air source heat pumps and their efficiency. These factors include airflow, ducts, and refrigerant charges.
Heat pumps need as much as 500 cubic feet (14.16 cubic meter) per minute of airflow to generate 1 ton (907.19 kg) of heat. The less airflow, the worse efficiency per head on the pump can create.
This problem often comes from the evaporator coil or fan speed, which a technician can fix.
Other times it comes from the ducts, which would require more insulation to prevent refrigerant leaks. Technicians should routinely check for this reason. Besides leaking, the refrigerant needs to generate the correct charge for the system to measure the right amount of refrigerant to work as efficiently as possible. Too little refrigerant measured, then too little airflow.
All air source heat pumps typically have EnergyGuide labels or equivalent.
These labels show the efficiency rating compared to other brands and models. The numbers are in BTUs and watt-hours.
For heat pumps in the winter, it’s the heating season performance factor (HSPF). This measurement looks at the total heat provided to a set area over a season compared to how much energy it consumes. This rating matters more in cooler climates.
For the summer, energy ratings measure the seasonal energy efficiency ratio (SEER). It looks at the total heat removed from a set area over a season compared to how much energy it consumes. This rating matters more in warmer climates.
The better the rating, the more expensive the air source heat pump can be initially.
However, increased efficiency in converting the electrical power source into heat can mean lower electricity costs over the lifespan of the heat pump.
Air source heat pumps transfer heat by working with two rules of physics: high pressure moves to lower, and heat moves to cold.
Step-by-step, this means heat pumps while in heating mode:
- Uses electricity as the sole power source.
- The air moves over the expansion device or evaporator coil.
- The evaporator coil absorbs the heat from the air to the refrigerant.
- Heated refrigerant turns to gas.
- A compressor adds pressure to gas and elevates the temperature.
- Through the refrigerant, the heat gets to the condenser coil.
- At the condenser coil, the heat is released into the new location, whether that’s or air to air heating or air to water.
- With the release of heat and pressure, the refrigerant cools and returns outside to restart the cycle.
See our complete guide to how an air source heat pump works for more information.
Air source heat pumps transfer heat inside or outside to moderate a building’s heating and cooling more efficiently than conventional system types using conversion and ignition.
Heat pumps are electrical appliances and can heat and cool an interior area.
They operate much like refrigerators and run fans that circulate refrigerant, which transfers the precise degree of heat and cold desired.
Air source heat pumps don’t need any other form of fuel like traditional gas/oil furnaces/boilers but require sufficient airflow and the temperature to be at a reasonable level.
Air Source Heat Pump Electrical Requirements
Parts Of An Air Source Heat Pump Explained
How Much Electricity An Air Source Heat Pump Uses
How Much An Air Source Heat Pump Costs To Run