An air source heat pump (ASHP) works by absorbing heat from the air outside your home. This heat can then be used to heat water, radiators, under-floor heating systems or warm air convectors.
The pump works in the same way as a fridge removes heat from the air inside it and it can extract heat at temperatures as low as minus 15ºC! These pumps do use electricity, so they do have a carbon footprint, but the heat they collect is being constantly renewed.
The upsides of air source heat pumps
• Lower fuel bills, particularly if you are replacing electric heating
• You can earn some income though the government’s Renewable Heat Incentive (RHI)
• Smaller carbon footprint
• No fuel deliveries and storage
• Low maintenance
• You can heat your water, or your home, or both
Heat pumps work at lower temperatures over longer periods of time, so you’ll need to keep them on all the time over winter. Your radiators won’t feel hot, like they do with a gas boiler.
How do these pumps work?
Heat from the air is absorbed into a fluid, which is then compressed, raising its temperature. This increased heat is transferred to the house’s hot water or heating circuits.
I’m interested, but is an ASHP for me?
Ask yourself:
Is there space for it? It needs to be placed outside your house with plenty of clearance for air to circulate around it. A sunny wall is the best place.
Are you well-insulated? ASHPs work best when producing less heat than traditional boilers, so any heat you get needs to be retained.
What’s your current fuel? If it’s gas central heating, your ASHP won’t pay for itself as quickly as if you’re replacing coal central heating or electrical heating.
What heating system will you use? ASHPs work best with under-floor heating systems and warm air systems rather than radiators because of the lower temperatures.
Are you buying a new build or having extensive work done? If so, the pump and new system can be installed alongside the other work, saving money.
What does it cost to install?
ASHPs cost between £7,000 and £11,000, while running costs vary with house size, how warm you want to be and how well-insulated your home is.
How much will I save?
This depends on what you’re replacing and what you’re replacing it with.
If possible, under-floor heating is better than radiators as it needs lower temperatures. If you can’t do this, then large radiators work well.
You’ll pay for the electricity used to run the pump, but you won’t pay for fuel any longer.
If your old heating system is inefficient, then a new pump will make a difference.
If you’re heating water too, then your heating system will be less efficient and you may need a solar water heating system.
This annual savings table is for a four-bedroomed detached house in England, Scotland or Wales with an average-sized air source heat pump.
•Gas older (non-condensing) – £295-£425
• Electric (old storage heaters) – £715-£1,295
• Oil older (non-condensing) – £360-£555
• LPG older (non-condensing) – £1,200-£1,805
• Coal – £525-£875
You could receive £905-£1,365 in payments from the Renewable Heat Initiative.