A complete guide to air source heat pumps

Thinking about installing an air source heat pump? Or wondering how much an air-source heat pump costs? Find out all you need to know about this low carbon heating alternative. 

Already decided on an air source heat pump?

What is an air source heat pump?

Air source heat pumps available with the Renewable Heat Incentive

Most home heating systems either burn fuel or convert electricity into heat. But heat pumps are different because they don’t generate heat.

Instead, they move existing heat energy from outside into your home. This makes them more efficient. Since they deliver more heat energy than the electrical energy they consume. So a heat-pump system typically costs less to run than a traditional heating system too.

How does an air source heat pump work?

An air source heat pump works much like a fridge operating in reverse to heat your home. Here's how it works:

How an air source heat pump works by pulling in outside air, which warms up tubes with liquid, which in turn changes to gas. The gas is compressed and passes to heat exchanger.
  1. Outside air is blown over a network of tubes filled with a refrigerant. This warms up the refrigerant, and it turns from a liquid into a gas.

  2. This gas passes through a compressor, which increases the pressure. Compression also adds more heat – similar to how the air hose warms up when you top up the air pressure in your tyres.

  3. The compressed, hot gases pass into a heat exchanger, surrounded by cool air or water. The refrigerant transfers its heat to this cool air or water, making it warm. And this is circulated around your home to provide heating and hot water. Meanwhile, the refrigerant condenses back into a cool liquid and starts the cycle all over again!

Using an air source heat pump at home

Air source heat pumps can be used to heat up your home and water. Here are some things to consider.

 

Using an air source heat pump for heating

Heat pumps work best when there’s less of a difference between the inside and outside temperatures. In much the same way that your fridge has to work harder in hot weather.

This makes them a good match for underfloor heating systems. Floors cover a much bigger area than radiators so they don’t need to get as hot to provide the same amount of heat.

Air source heat pumps also have a lower output than a gas or oil-fired boiler. This means they can’t deliver heat as quickly. Instead, they’re best used to heat your home up slowly over a longer period.

 

Air source heat pump and radiators

If you have radiators in your home, and you’re switching from a gas-fired heating system to an air source heat pump, you’ll probably need to buy some bigger radiators to keep your house toasty.

 

Using an air source heat pump for hot water

Heat pumps can also be a great source of hot water – but the water will be cooler than from a boiler. Practically this means that If you’re running a bath, you’ll need more hot water and less from the cold tap. So you’ll likely need a bigger hot water tank to cover your needs too.

Air source heat pump pros and cons

Air source heat pump advantages

  • Highly efficient source of heat and hot water

  • Zero carbon if used with a renewable tariff

  • Can closely match the running costs of other home heating systems

  • Installation cost offset by Renewable Heat Incentive payments

  • Low-maintenance with a long service life

  • Some systems can provide cooling in the summer

 

Air source heat pump disadvantages

  • Lower output temperature than conventional boilers – you may need to update your insulation and invest in bigger radiators too

  • May work best in older homes as part of a hybrid system with a conventional boiler

  • Need outdoor space, and can be noisy

  • Expensive to install and works best with a water tank

  • Don’t work as efficiently in extremely cold weather

 

Are there different types of air source heat pumps?

Yes! There are two main types of air source heat pumps, 'air-to-air' and 'air-to-water'. Most air source heat pump installations in the UK are what’s known as ‘air-to-water’ types.

There is also a hybrid air source heat pump which can often be combined with an existing central heating system and boiler. In these hybrid air-source heat pump systems, the heat pump provides a ‘base load’ for the day-to-day heating and hot water. With the boiler only firing up to provide hotter water. Or a quick heat boost during a particularly cold snap.

What is the cost of air source heat pump installation?

An air source heat pump costs more than a new gas or oil-fired central heating system. The typical cost ranges from £4,000-8,000, depending on the pump brand and its heat output.

You’ll also need to pay for the installation cost. This could bring the total to between £5,000 and £10,000. If you’re fitting new underfloor heating or an air distribution system, you’ll need to factor in these costs too. And potentially improved insulation, since air source heat pumps aren’t very effective at heating draughty or poorly-insulated homes.

What is the running cost of air source heat pumps?

Is there funding or a grant for air source heat pumps?

Are there any maintenance costs to air source heat pumps?

hybrid heat pump being inspected

Air source heat pumps use well-established technology and may have a working life of 20 years or more. But just like a boiler, you should get your air source heat pump professionally serviced – every two or three years (or annually, if you have a compressor inside your home) – to make sure that it’s still working at its best. There are some things you can do yourself:

  • Be sure that there’s a plentiful supply of air. This means regularly checking for leaves or rubbish caught in the fan’s grilles. And pruning back any plants growing too close to the unit or its pipes.
  • In very cold weather clear snow from the air source heat pump and check that the grilles aren’t blocked by ice.

How to get an air source heat pump

Air source heat pumps are best suited to well-insulated homes, ideally working alongside technologies like underfloor heating. Your home also needs to have outside space.