Air Source Heat Pump
An air source heat pump (ASHP) is a renewable and low carbon way to heat your home. It works like a traditional central heating system, but instead of burning oil or gas, it extracts heat from the air outside.
Depending on the type of heat pump you have, it can also provide hot water for your home. Although it works a little differently from a boiler, it can keep your home comfortable throughout the year.
This guide explains how an air source heat pump works. It will also help you decide whether an air source heat pump is right for your home.
What is an air source heat pump?
An air source heat pump (ASHP) is a type of central heating system that uses heat from the air outside to warm your home. It works by heating water, which is then circulated through your radiators.
If your system includes a hot water cylinder, it can also provide hot water for your kitchen, bathroom and other household needs. Although it works differently from a traditional boiler, an air source heat pump can provide reliable heating and hot water throughout the year.
How does an air source heat pump work?
Put simply, an air source heat pump takes warmth from the air outside, increases it, and uses it to heat your home. It can do this even when the weather is very cold. In fact, most heat pumps can still heat your home in temperatures as low as -15°C.
Most air source heat pumps are connected to a wet central heating system. This means the heat pump warms water, which then circulates through the pipes in your home and heats your radiators or floor. These systems are known as air-to-water heat pumps because they transfer heat from the air into water.
Some homes have an air-to-air heat pump instead. These systems warm rooms by blowing heated air through indoor fan units. These systems are more suitable for smaller homes.
Pros and cons of an air source heat pump
- Up to 400% efficient
- Low carbon
Could save you money on your heating bills, depending on your current system and tariffs
- You’ll probably need to upgrade some of your radiators
- Less efficient in poorly insulated homes
- Space needed for the outdoor unit and the water cylinder indoor
Is an air source heat pump right for my home?
Like all heat pumps, an air source heat pump works best in a home that is well insulated. Good insulation helps keep the heat in, making your home more comfortable and helping your system run efficiently.
Many homes can also benefit from larger radiators. Because heat pumps work at lower temperatures than traditional boilers, radiators with a larger surface area will help spread heat more effectively around your home.
If you would like your air source heat pump to provide hot water as well as heating, you will usually need a hot water cylinder. The size of the cylinder will depend on your household's hot water needs and the space available in your home.
If you have limited space, a heat battery may be a suitable alternative to a hot water cylinder. Your installer can help you decide which option is best for your home.
Air source heat pump location
Before choosing an air source heat pump, it is important to check that you have enough space for the system.
The outdoor unit needs to be installed outside your home, either on the ground or mounted on a wall. To help it work efficiently, it should not be placed in a corner. Where possible, it should be positioned away from bedroom windows.
The unit also needs enough clear space around it so that air can circulate freely. Your installer will be able to advise on the best location.
There are two main types of air source heat pump:
- Monobloc systems, where all the main components are contained within the outdoor unit.
- Split systems, which have both an outdoor unit and an indoor unit.
If you choose a split system, you will need space indoors for the additional unit. This is typically about the size of a small fridge.
Planning permission for air source heat pumps
Most homes don’t need planning permission for an air source heat pump. However, if you live in a conservation area or listed building, you’ll need to get in touch with your local authority to check the rules.
Will air source heat pump heating save me money?
Most of the heat used by an air source heat pump comes from the air outside, which is free. However, the system does use electricity to operate the pump, so there are still running costs to consider.
The good news is that heat pumps use electricity very efficiently. Under the right conditions, an air source heat pump can produce around 4 units of heat for every unit of electricity it uses. Even in colder weather, when temperatures fall below freezing, a heat pump can still provide around twice as much heat energy as the electricity it consumes.
How much money you could save by switching to a heat pump depends on several factors, including:
- The type of heating system you are replacing, such as electric heating, oil, gas or LPG.
- The price you pay for electricity and the tariff you are on.
- How energy efficient your home is.
As a general guide:
- Homes currently heated by electric storage heaters often see significant savings after switching to an air source heat pump.
- Homes heated by older or less efficient boilers may also benefit from lower running costs.
- If you already have a modern, highly efficient gas, oil or LPG boiler, the running costs could be similar.
A heat pump installer can help you estimate the costs and potential savings for your home based on your current heating system and energy use.
How much does an air source heat pump cost?
The cost of an air source heat pump will vary, depending on:
- the size and model of the heat pump
- the size of your home
- whether you need to upgrade other parts of your heating system (e.g. radiators)
The average cost of installing an air source heat pump is £12,500. We’d recommend getting at least three quotes from different installers before making a decision.
Air source heat pump grants and funding
Boiler Upgrade Scheme (BUS)
The Boiler Upgrade Scheme or "BUS", is a government initiative that offers grants to help property owners replace their fossil fuel heating systems with heat pumps or biomass boilers. The scheme aims to reduce carbon emissions, energy bills, and fuel poverty. The scheme is funded by the government and the major energy suppliers and administered by Ofgem.
We think this fund might help you with the upgrades your home needs. You should contact some local MCS accredited heat pump installers. We recommend getting three quotes.
The cost of installing a heat pump usually exceeds the value of the grant and may cost you more than replacing a gas boiler. The bills are likely to remain similar, but it would result in a significant reduction in carbon emissions.
To find out more, visit https://www.gov.uk/apply-boiler-upgrade-scheme
Air source heat pump FAQs
With regular scheduled maintenance you can expect an air source heat pump to operate for 20 years or more.
Air source heat pumps require maintenance like any other central heating system to ensure it remains safe and operates efficiently. Some maintenance is straight forward and can be carried out by the householder, but other maintenance should be done by a professional. Typical maintenance includes:
- A yearly check that the air inlet grill and evaporator are free of leaves or other debris.
- Detailed check by a professional installer (typically every year).
- Removal of any plants that have started to grow around the heat pump.
- Check the central heating pressure gauge in your house from time to time. You will be shown how to do this by the contractor.
- Use anti-freeze in colder weather to prevent the heat pump from freezing. Levels of anti-freeze and its concentration vary but this will be explained to you by the contractor.
A small amount of noise is produced from the fan within an air source heat pump while it is in operation. The noise is minimal and shouldn’t be disruptive. Typical air source heat pumps have noise levels of around 45dB(A). For comparison, a typical library has a noise level of around 40dB(A).
This depends but the average installation on site can take between 2-5 days. The level of disruption varies, according to how many radiators need replacing, as well as the position of the indoor and outdoor units.
Many homes benefit from larger radiators, because heat pumps work at lower temperatures than traditional boilers. Radiators with a larger surface area will help spread heat more effectively around your home.
Yes. You could combine heat pumps with other technologies to maximise your carbon savings and minimise your energy bills. For example, solar PV could be used to generate the electricity that powers the heat pump, and if this was coupled with a battery, stored power from the PV panels during the day could heat your home and the domestic hot water at night.
Want to find out more?
Want to know if an air source heat pump will work for your home? PEC can help.
Our Future Fit services provide independent, expert advice on the suitability of a heat pump for your property and how they can fit into a wider home upgrade.
If you are just starting out on your retrofit journey, a free Home Visit is the easiest way to explore what’s possible for your home.
If you are ready to make your home feel even better choose a Future Home Survey for a detailed retrofit plan tailored to your home.
Visit our Retrofit Services page to find out more about how we can help.