How efficient are air source heat pumps?

Air source heat pumps are one of the most efficient ways of heating your home, generating three times the amount of heat compared to a traditional gas boiler, due to being 300% more efficient in comparison.

They are a sustainable, low-carbon option to heat your home and hot water, helping you save energy and money.

By installing an Air Source Heat Pump – you can: 

• Increase Energy Efficiency by 300% (1) 

• Reduce Carbon Emissions by 80% (2) 

• Save £240 a year on energy bills (3) 

Several things effect heat pump efficiency, including:

It has been written in the media that air source heat pumps are not suitable for the UK winter climate. Put simply, this isn’t true.

We’ve discussed in depth how your heat pump works by absorbing energy from the air outside and converting it to heat your home and hot water even in below-zero temperatures so there really shouldn’t be anything to worry about when the weather gets colder.

In the winter, your air source heat pump works no differently. Your heat pump is perfect for the UK climate because it can work off-grid and still operate when outside temperatures are as low as -15C. Even in freezing cold temperatures, air contains thermal energy and air source heat pumps absorb this heat and transfer it to your home using refrigerant which will boil even in sub-zero temperatures.  In short, your air source heat pump works the same in winter as it does throughout the rest of the year, it will just work a little harder in the winter months in the same way that your old gas boiler did.  Your external heat pump is also a sealed unit that has been designed to withstand all the weather conditions that the UK climate can throw at it so there really is nothing to worry about.

In summary, a well-designed air source heat pump system, tailored to your property and local climate will keep you warm in winter, and provide you with all the hot water you need with no disruption to your daily life even in the coldest winter months. 

Running costs can vary on several factors such as your energy tariff, and the performance of your heat pump.  With current electricity prices, the costs of running an air source heat pump will be similar to your average gas boiler.

If you’re replacing an older, G-rated gas boiler, you could save around £240 a year on your energy bills (4). 

There are also ways to save even more by switching to a heat pump tariff like the EDF heat pump tariff where you pay less for running your air source heat pump at certain times.

There are several things you can do to keep your air source heat pump running at maximum efficiency, including:

• Ensure your radiator thermostat valves (TRVs) are set to their highest setting.
• Make sure you bleed your radiators when you need to.
• Ensure weather compensation is set up correctly. 
• Leave your air source heat pump turned on all year round.
• Ensure your hot water schedules are set up correctly. 
• Keep windows closed on colder days (reducing heat loss).
• Don’t alter the settings of your air source heat pump without first consulting an expert.
• Look at dedicated energy tariffs which make running costs cheaper.
• Look into the benefits of solar panels to power your home and heat pump.
• Keep it clear from snow, debris, and obstruction, allowing for good airflow.  

Yes, they can.

Air source heat pumps can be 300% efficient, if not more in some cases.

Heat pumps can produce 3kw of energy for every 1kw of electricity used – this is known as the Coefficient of Performance (CoP).  So, if a heat pump has a CoP of 3.0, then it gives out three units of heat for every unit of electricity it uses. 

By comparison, a gas boiler will use 1kw of gas to create 0.85kw energy so you can instantly see how much more efficient an air source heat pump heating system is compared to a traditional gas-fired heating system.

How is this possible?

Gas boilers produce energy by burning fuel (a volume of gas is ignited, and a certain amount of energy is released). This means you can’t ever release more energy than is stored in that volume of gas. This means a fuel-burning system can never achieve more than 100% efficiency.

For example: if you ignite some wood in a fire, you can’t get more energy than you have with that wood without adding more wood. You burn the fuel, you get heat, the fuel is gone, no more energy! 

Air source heat pumps don’t create heat, they extract energy from the air to change the state of the refrigerant which is then compressed to produce heat. This useful heat is then transferred to the water that runs around the central heating system.  Because they don’t have to burn a fuel, their efficiency depends on how well they’re able to move energy from one place to another.  As technology improves, there’s no theoretical maximum to how efficiently you can move energy. This means we could see systems getting to be four, five, or ten times more effective at moving energy in the future. It’s simply an engineering problem! But for now, they are one of the best alternatives to traditional gas boilers in terms of efficiency, savings, and sustainability.

Yes, your system may be less efficient in the winter, but it will still keep you cozy and warm. 

MCS requirements mean that all systems must be designed down to sub-zero temperatures which is more than adequate for the UK climate. Furthermore, each system is designed to keep your home warm in freezing temperatures.

If you live in a cold area and the temperatures drop below zero, you will see efficiency impacted but it certainly won’t leave you out in the cold. Most air source heat pumps are designed to work in temperatures of up to -15C.  The average UK temperature in the winter ranges from -2C to -7C so your heat pump will be more than able to cope with the UK climate and cold weather. 

Most of today’s heat pumps have a built-in defrosting and de-icing setting which keeps the fans clear so that your heat pump is always working when you need it. Never pour boiling water over your heat pump to defrost it. Your heat pump is an electrical appliance and doing so is highly dangerous and will damage your unit.

If you are impacted by snow, it never hurts to pop outside if you can, and make sure that the snow is away from the outside unit in much the same way as you would go out and keep your drive and paths clear from snow to access your house.

You could also consider a custom-built cover that has been specifically designed for your air source heat pump. We do not recommend making one yourself as you could block the airflow of the unit so have a chat with your installer about the options available to you.

In short – yes.

Much like any heating system, your energy consumption will be more in colder months, due to outside temperature and the heat loss profile of your home (the rate in which your property loses heat).  An air source heat pump is like any other heating system in those colder months. As your home loses more heat, more heat is required to keep it warm.  

In winter you can expect your heat pump to use more energy (just like your existing boiler) and see an increase in your energy bill (depending on what kind of tariff you are on). The important thing to consider is that over the year, you would have still used 3x less energy than a boiler and saved some money too.  

Remember – Even if the savings on your energy bill are not enough to win you over, you are still reducing carbon and energy consumption, leaving a better world behind for future generations. Fitting your home with the latest technology can also increase its value. 

If you’re making the switch to an air source heat pump, you’ll be moving to a fossil-free system. Your air source heat pump will draw energy (heat) from the air around it.

When we talk about the energy used by an air source heat pump system, we’re talking about the energy required to operate it and extract the required heat from the air.  For Example – Heat pumps use 1kW of electricity and produce 3kw of heat. A household that uses 12,000kw of gas a year, will only need to use 4,000kw of electricity to produce the same amount of heat – that’s a huge saving on energy and carbon.  

Currently, electricity prices are higher than gas which means that the costs of running an air source heat pump will be similar to your average gas boiler. If you’re replacing an older, G-rated gas boiler, you could even save around £240 a year on your energy bills (4). 

However, there is a way to save even more. Switching to a heat pump tariff (like the EDF Heat pump tariff) means you pay less for running your heat pump at certain times reducing the cost of your electric bill.  With some clever scheduling of your hot water and smart meter, you can be money-savvy and save even more with your heat pump running costs.  

If you have solar panels, an air source heat pump could be the perfect choice. The power (electricity) that is produced can also be used to power your heat pump so you can reduce your energy bill even more. 

The average cost of an air source heat pump installation (including design, parts, and labour) is £6,100 inclusive of government grants such as the Boiler Upgrade Scheme.  A heat pump could cost you less than this or more, depending on a variety of factors.

While the upfront costs may be higher than a gas boiler, air source heat pumps have a much longer life span and a much greater level of efficiency.  Running costs for a heat pump also vary and factors such as your energy tariff, type, and size of system are a few of the variables that impact running costs. The benefits of an air source heat pump system, and the savings it will ultimately generate, will far outweigh the initial outlay costs over time. We explore more about costs in our dedicated costs page. 

We’ve been installing air source heat pumps for over 20 years now and know what happens when a system is poorly designed or installed. We’ve learned a  lot about heat pumps in these 2 decades. 

So, if you’re just starting to look into the options, or have a few questions. Save yourself some time. Give us a call or fill in a form.  

(1) (2) Annual heating demand of 25,000kWh; average heat pump SPF of 2.64; gas boiler efficiency of 84%; mains gas carbon emissions 0.21kg CO2e per kWh; electricity carbon emissions of 0.136kg CO2e per kWh; vehicle emissions of 225g CO2e per mile; average driving distance of 7,400 miles per year. https://energysavingtrust.org.uk/case-study/raj-and-his-familys-air-source-heat-pump/ 

 (3) Potential annual savings of installing a standard air source heat pump in a three bedroom semi-bedroom detached home, with radiator upgrades as required. https://energysavingtrust.org.uk/advice/air-source-heat-pumps/ 

 (4) Figures are based on fuel prices as of July 2024 (October 2023 for NI). Find out more about these calculations.  The running cost you can expect will depend on the size of your home, any heating system upgrade and any saving will also depend on the fuel type being replaced. You can expect the saving to range between old and new, depending on the age of your current heating system.