Pros and Cons of Air Source Heat Pumps
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. This works via the wet central heating systems to heat radiators and provides domestic hot water. Heat pumps work similarly to a refrigerator: they absorb heat and transfer it to another medium.
Certain air source heat pumps can also work as a cooling system in the summer months. Most commonly they are placed outside of a building where there is adequate space for the installation.
There are two main 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).
Before making the switch, consider both the advantages and disadvantages of air source heat pumps.
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 and reduces the burden of air source heat pump costs.
10 Advantages of Air Source Heat Pumps
There are numerous benefits to using heat pumps. 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.
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. For every 3 to 4 units of energy produced from an air source heat pump, only 1 unit of electricity is used, making it a far better alternative to cut 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. Although the upfront cost is fairly high, you will be eligible to receive a significant portion of your investment from RHI payments. You can save up to £1,335 with an air source heat pump.
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. All you need to check is that the COP of your air source heat pump should be above 0.7 for cooling.
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 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.
High Seasonal Coefficient of Performance (SCOP)
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. A domestic air source heat pump typically doesn’t require planning permissions, but it is always advised to check with the local authority before you start your process. It's an ideal option for both retrofits and new builds. If you are combining air source heat pump installation with other building work, you can also bring down the cost of installation.
Servicing and maintenance should be done by a technician once a year. As such air source heat pumps are low maintenance, but 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. With several technological developments modern heat pumps are able to work efficiently for close to 25 years before they need replacing.
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.
6 Disadvantages of Air Source Heat Pumps
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. Also, another common problem with air source heat pumps is that they can be noisy. So, choosing where to position them can make a big difference.
These are the main air source heat pump disadvantages:
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. This is because they exclusively depend on outside air and as the temperature drops, so does the overall heat output that the pump can produce.
Ground source heat pumps on the other hand have pipes buried deep under the ground and have a more stable temperature and are little affected by cold climates.
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. It remains that heat pumps are a heavy investment for many. However, the future of UK is focusing on increasing heat pump installations significantly and you can expect to have more low carbon incentives to make the switch.
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.
- Installer: Finding the right installer is very important to ensure the heat pump is installed correctly. You should do your due diligence, such as checking if the installer has the necessary accreditations, a positive track record, and that you are being given a fair price.
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.
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