What Is an Air Source Heat Pump?
An air source heat pump (ASHP) works by transferring heat absorbed from the outside air to an indoor space, such as a home or an office via the wet central heating systems to heat radiators and provide domestic hot water. Heat pumps work similarly to a refrigerator: they absorb heat and transfer it to another medium.
The interactive graphic below illustrates how the process works. You can click each point to read about the steps in more detail:
Certain air source heat pumps can also work as a cooling system in the summer months. Air source heat pumps are placed outside of a building where there is adequate space.
2 Types of Air Source Heat Pumps
- Air to air heat pumps, which absorb heat from the outside air and then transfer it directly into your home via a fan system to heat a room.
- Air to water heat pumps, which absorb heat from the outside air and then transfer it via your central heating system to provide hot water heating, radiator, or underfloor heating in an indoor space (or all three).
What Are the Advantages and Disadvantages of ASHPs?
Air source heat pumps are a renewable alternative to heat your home in the UK. With an air source heat pump, you can save money on your energy bills and reduce your carbon footprint compared to a gas or electric heating system.
One of the key advantages of air source heat pumps is their versatility and affordability. An ASHP can work for either heating or cooling purposes and can be used for space heating or water heating. In order to achieve Net Zero by 2050, the UK government aims to install 19 million heat pumps in new builds. With the increase in heat pump deployment, the UK government grants make this renewable energy source even cheaper to run.
An important disadvantage to be aware of is that air source heat pumps have a lower heat supply than other alternatives. This means you would get the most out of your ASHP, you need to have a well-insulated home and, ideally, underfloor heating, too.
Before making the switch, consider both the advantages and disadvantages of air source heat pumps.
12 Advantages of ASHP are:
ProsRead the all 12 pros of air source heat pumps in the section below.
- Low carbon footprint
- Save money on energy bills
- Eligible for RHI
- Can be used for both heating and cooling
- Can be used for space heating and domestic hot water
- Can work even in lower temperatures
- High Seasonal Coefficient of Performance (SCOP)
- Easy installation process
- Low maintenance
- Long lifespan
- No fuel storage neede
- Can be powered by wind or solar energy
7 Disadvantages of ASHP are:
ConsRead all 7 cons of air source heat pumps in the section below.
- Lower heat supply than boilers
- Extra spending to install underfloor heating
- Your home must be well insulated already
- Lower efficiency below 0°C
- Lower savings compared to low price mains gas
- Electricity is needed to run an ASHP
- ASHPs can be noisy
12 Advantages of Air Source Heat Pumps
The most important advantages of purchasing an air source heat pump are the following:
Low Carbon Footprint
Air source heat pumps have are a form of low carbon heating, as they use the outside air to heat or cool your home. If you are switching from a coal- or electricity-based heating system, you can significantly reduce your carbon emissions.
Save Money on Energy Bills
By switching to air source heat pumps, you can reduce your energy bills as you’ll be using the outside air for your heating and cooling needs. Your savings will be more significant if you are going from an electric or coal-based system.
The running costs of heat pumps depends on a few factors, from the efficiency, to the amount of heat needed, and the temperature of the heat source.
Eligible for RHI
You could receive payments by generating your own heat through the Renewable Heat Incentive. By making use of this green energy grant, you can save even more on your energy bills.
Air-to-water heat pumps are eligible for the domestic RHI and the scheme has been extended until March 2022. This means, if you install your heat pump within that deadline, you will receive payments for each unit of heat generated for a period of 7 years. The domestic RHI payments are calculated based on the current RHI tariffs, your heat pump’s SCOP, and of course, your energy demands.
Other types of heat pumps are also eligible for RHI payments.
Can Be Used for Heating and Cooling
Air source heat pumps can be used for both heating and cooling purposes. Depending on the model, they can provide cooling in the summer and heating in the winter.
In addition, air source heat pumps work very well with underfloor heating — so if you want to get the most out of your system, you should strongly consider installing underfloor heating.
Can be Used for Space Heating and Domestic Hot Water
Depending on the air source heat pump, you can also use it to heat your water. This depends on the temperature of the water in the heating system (also known as 'flow temperature'). To be able to heat water, the flow temperature needs to be approximately 55°C. If your system is only designed for space heating, the flow temperature will be 35°.
If you are looking for both space heating and water heating, then opting for an ASHP that has a flow temperature of 55°C is needed.
Can Work Even in Lower Temperatures
An air source heat pump can extract heat from the ambient air even at a lower temperature, down to -20°C. What is more, heat pumps are known to work efficiently in severely cold countries such as Canada. Success stories reveal an air-to-air heat pump can generate 40°C heat when outside temperatures are as low as -30°C.
High Seasonal Coefficient of Performance
Air source heat pumps are efficient both in the winter and summer, thanks to an outstanding SCOP (seasonal coefficient of performance). The COP of a heat pump is a way to measure its efficiency by comparing the power input needed to produce heat to the amount of heat output. A 'seasonal COP' figure is adjusted to seasonality.
For example, a typical air source heat pump runs at a COP 3.2 when the outside temperature is above 7°C. This means that the heat pump is 320% efficient: for each kWh of electricity used by the fans and the compressor, 3.2 kWh of heat is generated. The higher the COP, the better.
Therefore, when considering an air source heat pump's COP vs outside temperature, then you will find that despite some slight fluctuations, they can run efficiently year-round. To be able to compare heat pumps based on how much they are affected by these efficiency changes, the seasonal COP is used.
Easy Installation Process
Installing an air source heat pump can take as little as two days. Installing an air source heat pump is easier than installing a ground source heat pump, because you don’t need to dig. An air source heat pump typically doesn’t require any planning permissions, but it is always advised to check before you start your process. It's an ideal option for both retrofits and new builds.
Servicing and maintenance should be done by a technician once a year. There are a few things that you can do to ensure optimal performance of your heat pump, from cleaning filters, to checking for system leaks, checking refrigerant levels, clearing leaves and dust from your heat pump, and so on. Any more technical tasks should only be done by a certified installer.
Air source heat pumps have a long lifespan, and with proper maintenance, they can be operational for up to 20 years. What’s more, is that most air source heat pumps have 5-year warranties.
No Fuel Storage Needed
No fuel storage is needed with air source heat pumps, because the fuel used is the outside air. With oil-fired boilers, for example, you need to store the oil somewhere, which would take up extra space on your property. Not relying on fuel, such as oil or wood pellets, also means you won’t have to pay additional fees for fuel deliveries.
Can be Powered by Wind or Solar Energy
Air source heat pumps can be powered by wind or solar energy instead of electricity from the grid. Most heat pumps are considered semi-renewable, as electricity is still required to run the system. However, if you combine heat pumps and solar panels, you can make your home even more sustainable.
7 Disadvantages of Air Source Heat Pumps
The main air source heat pumps disadvantages are as follows:
Lower Heat Supply than Boilers
This type of heating has a lower heat supply compared to oil and gas boilers, so larger radiators might be needed. The water that is circulated within radiators that are hooked up to boilers might operate at a higher temperature than those of an ASHP system.
So, for the same amount of space heating, you will need a larger heat emitting surface.
Extra Spending to Install Underfloor Heating
Due to the lower heat supply, air source heat pumps are most commonly used with underfloor heating to get the most out of the system. This is because you will not need as high temperatures to operate this — you won’t want to stand on a 40°C floor.
This can mean that your installation costs may be higher if you do not already have an underfloor heating system installed.
Your Home Must Be Well-Insulated Already
In order to reap the full benefits of an air source heat pump, you will need a well-insulated home to begin with. However, this is true for any heating system.
If heat can easily escape from your home through windows, doors, or through walls, then you will need more energy to keep the space warm. Therefore, ensure your home is insulated well enough.
Lower Efficiency Below 0°C
Although air source heat pumps can work at temperatures as low as -20°C, they do lose efficiency below 0°C.
Lower Savings Compared to Low Price Mains Gas
If you have access to cheap mains gas, then the difference between the gas price and the electricity price (for powering an air source heat pump) won’t be significant.
Electricity Is Needed to Run ASHP
Air source heat pumps need electricity to run, making them only semi-renewable. This can be a disadvantage for some if they are looking to make their home entirely green.
If you need to have your heat pump on year-round, then you will naturally not see as significant drops in your energy bill as you would if you paired your heat pump with a solar panel, for example.
ASHPs Can Be Noisy
Air source heat pumps can be somewhat noisy when they are running, comparable to a regular air conditioner or light to heavy rain. However, companies are continually making technological advancements to improve this and reduce their noisiness.
What to Take Into Account Before Installing an ASHP
When thinking about installing air source heat pumps, one must consider two main factors:
- Costs: The cost of installing an air source heat pump is usually between £8,000- £18,000. Additional costs may be incurred depending on the chosen system type (whether you need cooling in combination with heating), the size of your property, and your specific requirements. These costs are much lower compared to ground source heat pump prices, which range from £20,000 - £45,000.
- Insulation: To have high returns in terms of saving, it is important to have a well-insulated home, particularly with loft insulation. This ensures that the heat generated within the home does not escape, thus allowing for a consistently warm home during the winter.
There are many advantages of heat pumps, and air source heat pumps in particular can work well if you have a well-insulated home with an underfloor heating system ready.
If an air source heat pump sounds interesting to you and you are considering buying one, simply fill in the form above to get up to 4 personalised, no-obligation quotes, leading you a step closer to becoming a future owner of an air source heat pump.