Air Source Heat Pumps

Air source heat pumps absorb heat from the outside air. This heat can then be used to heat radiators, underfloor heating systems, or warm air convectors and hot water in your home. An air source heat pump extracts heat from the outside air in the same way that a fridge extracts heat from its inside. It can get heat from the air even when the temperature is as low as -15° C. Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally.

How do air source heat pumps work?

Heat from the air is absorbed at low temperature into a fluid. This fluid then passes through a compressor where its temperature is increased, and transfers its higher temperature heat to the heating and hot water circuits of the house. There are two main types of air source heat pump systems.

Air-to-water An air-to-water system distributes heat via your wet central heating system. Heat pumps work much more efficiently at a lower temperature than a standard boiler system would. This makes them more suitable for underfloor heating systems or larger radiators, which give out heat at lower temperatures over longer periods of time.
Air-to-air An air-to-air system produces warm air which is circulated by fans to heat your home. They are unlikely to provide you with hot water as well.

The benefits of air source heat pumps

lower fuel bills, especially if you are replacing conventional electric heating
lower home carbon emissions, depending on which fuel you are replacing
no fuel deliveries needed
24/7 heat for your home as well as your water
minimal maintenance required
can be easier to install than a ground source heat pump

Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. During the winter they may need to be on constantly to heat your home efficiently. You will also notice that radiators won't feel as hot to the touch as they might do when you are using a gas or oil boiler.

Is an air source heat pump suitable for me?

To tell if an air source heat pump is right for you, there are a few key questions to consider:

Do you have somewhere to put it? You'll need a place outside your home where a unit can be fitted to a wall or placed on the ground. It will need plenty of space around it to get a good flow of air. A sunny wall is ideal.
Is your home well insulated? Since air source heat pumps work best when producing heat at a lower temperature than traditional boilers, it's essential that your home is insulated and draught-proofed well for the heating system to be effective.
What fuel will you be replacing? The system will pay for itself much more quickly if it's replacing an electricity or coal heating system. Heat pumps may not be the best option for homes using mains gas.
What type of heating system will you use? Air source heat pumps can perform better with underfloor heating systems or warm air heating than with radiator-based systems because of the lower water temperatures required.
Is the system intended for a new development? Combining the installation with other building work can reduce the cost of installing the system.

Is an air source heat pump suitable for your property?

The heat produced is typically between 35 and 45 degrees Celsius which is much lower than a conventional boiler. The heat pump should be incorporated with an under floor heating system and a solar thermal panel (to provide domestic hot water) for maximum efficiency. Air source heat pumps are not as commonly used here as ground source heat pumps but are starting to become familiar. They have been used in other parts of the world for some time. They are considerably cheaper than ground source heat pumps to install, as they don’t require any ground works and don’t require much space. This also makes them ideal for flats, apartments and dwellings with limited space. An air source heat pump should provide the heating requirements for a well insulated property in all but the most extreme conditions.

You may also want to consider ground source heat pumps, which use pipes buried in the garden to extract heat from the ground.

Costs

Installing a typical system costs around £7,000 to £14,000. Running costs will vary depending on a number of factors including the size of your home, how well insulated it is and what room temperatures you are aiming to achieve.

Savings

How much you can save will depend on what system you use now, as well as what you are replacing it with. Your savings will be affected by:

Your heat distribution system. If you have the opportunity, underfloor heating can be more efficient than radiators because the water doesn’t need to be so hot. If underfloor heating isn’t possible, use the largest radiators you can. Heat Pumps NI will be able to advise you on this.
Your fuel costs. You will still have to pay fuel bills with a heat pump because it is powered by electricity, but you will save on the fuel you are replacing.
Your old heating system. If your old heating system was inefficient, you are more likely to see lower running costs with a new heat pump
Using controls. Learn how to control the system so you can get the most out of it. You will probably need to set the heating to come on for longer hours, but you might be able to set the thermostat lower and still feel comfortable. Heat Pumps NI will explain to you how to control the system so you can use it most effectively.