Project Summary: How Air Source heat pumps capture energy from the air outside which can be used to heat water and your home.
Air Source heat pumps extract heat from the air outside your home and then concentrate it to a higher temperature. The pump then uses this heat to heat your home or hot water. These systems are normally used with under-floor heating, low temperature radiators or warm air convectors, substantially reducing your energy bills. Air Source heat pumps are easier to install than Ground Source heat pumps.
Heat can be taken from external air even when outside temperatures are as low as minus 15°C, but heat pumps do have a higher level of efficiency at slightly warmer temperatures than this. Air Source heat pumps currently qualify for the government’s Renewable Heat Premium Payment, which gives a one off payment of £850 towards installation costs, and may qualify for regular payments for heat generation through the Renewable Heat Incentive scheme to be confirmed in 2013. They are also eligible for whole or part funding through the Green Deal scheme which pays for the installation up front and should make the installation costs free to you.
They use some electricity to circulate the heat that they extract from the air outside around your home, but they will capture more energy than they use, and are more efficient than many other heating systems. They operate most effectively in more airtight and well insulated homes.
The savings that you can make on your energy bill with this technology depend on which type of fuel you are replacing, however the Energy Saving Trust trials suggest that homes using solid fuel or oil could make a saving of around £300. A 3 bedroom semi using electricity for heating and hot water could save as much as £610.
They are generally the size of a small air conditioning unit and are mounted on an exterior wall, ideally with a good air flow around it. Unlike a ground source heat pump you do not need any outside space to bury piping.
Heat pumps can only deliver heat of a temperature up to about 60°C efficiently, which means that they are most effective if they are left on all the time during winter months. They are most effective for heating when used with lower temperature radiators or under floor heating as they do not produce water as hot as gas fuelled systems and need a larger surface area to transfer the heat into the room.
Air source heat pump systems fall into two main categories, based on how they deliver the heat into your house:
Another type of heat pump that works on the same principle is the MVHR (Mechanical Ventilation and Heat Recovery) system, an exhaust-air-source heat exchanger which reclaims the heat from the air leaving from your home via vents. This is really only effective in modern air-tight homes.
In order to qualify for the Renewable Heat Incentive scheme the system should be installed by a MCS accredited installer. It is not necessary to bury piping in the ground outside as for the Ground Source heat pump, but you will need space on a wall outside to mount the air handling unit. They do make some noise, so take this into account when deciding where to place your unit. You can get the decibel rating of the unit checked and models with a cover are generally quieter.
Installing an air source heat pump is generally easier than other types of heat pump; however it is a good idea to think about how it will work with your current heat emitting system, particularly if you have water filled heating system.
You will need to think about the following:
Heat pumps are fairly energy efficient systems. They are capable of generating as much as 4 kilowatts of heat energy for each kilowatt of electricity they use to run. How efficient a heat pump is can be described using the term Coefficient of Performance (CoP). The CoP measures a heat pump’s ratio of heat output to energy input, so the higher the figure, the more efficient the pump.
The Energy Saving Trust has also come up with an additional measure known as the System Efficiency Ratio (SER). The SER describes the ratio of how many units of electricity the entire heating system uses to run compared to the number of units of heat the pump produces. Both the COP and SER range from around 1 to around 4. The Energy Saving Trust’s recent heat pump trials found that the mid-range SER for air source heat pumps was around 2.2, with the best units reaching 3.2.
You can also get the system all or part funded by the Green Deal scheme which pays for the installation up front. You then pay back this amount through payments on your energy bills, which including interest shouldn’t be larger than the value of the energy saving you make every month by using the technology. This effectively means that the technology is free to you and could even make you a saving. However, you will be paying interest on your installation costs which does reduce your savings compared with if you had paid for the installation up front. You can find out more about the Green Deal on our Green Deal page.
Installation can vary and will depend on the size of the system, the size of home or space you want to heat and the amount of hot water that you think you will need. It is ideal to combine it with other building work which might play a part in the time it takes too.
Always use an MCS accredited installer for this work. Only MCS accredited installers are able to sign off installations that will comply with the government’s Renewable Heat Incentive and Renewable Heat Premium Payment schemes.
Heat pumps normally come with a 10 year warranty and you should expect it to run for at least 20 years. The system should be checked every year and you should arrange to have a professional installer check it every 3-5 years.
You could save over £610 per year on your heating and hot water bills, though the amount will depend on your current heating system. You can also get a one off grant of £850 if the air source heat pump is fitted by an MCS accredited installer. There are some other benefits too:
The energy and money you save by installing the pump will depend on several factors:
Here are some other related projects that you might find useful: