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A complete guide to air source heat pumps

Thinking about installing an air source heat pump? Wondering how heat pumps work, or how much an air source heat pump costs?

Find out all you need to know about the low carbon heating alternative for 2024. 

Already decided on an air source heat pump?

What is an air source heat pump?

An air source heat pump works by absorbing heat from the environment, even when temperatures are well below freezing. It extracts heat from the air around us and transfers that heat to the inside of your home, keeping you warm and comfortable.

Discover the benefits of an air source heat pump

Did you know heat pumps:

  • use renewable energy
  • are more efficient than gas boilers (up to 300% more efficient)
  • can be cost effective
  • reduce your carbon footprint
  • are quiet

How does an air source heat pump work?

A heat pump works a bit like an inside-out fridge. It captures heat from outside and moves it into your home, using electricity to do so. Here's how it works:

  1. Outside air is drawn in over a network of tubes filled with refrigerant gas, which circulates at -28°c to extract heat energy from the air outside.
     
  2. The gas passes through a compressor which increases the pressure and temperature causing it to change from a cold gas to a hot liquid.
     
  3. The compressed hot liquid passes into a heat exchanger that heats water for both your radiator heating circuit and your taps. The refrigerant then turns back into a cold gas and starts the cycle all over again.
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.

Air source heat pumps work at a lower internal temperature than a gas or oil-fired boiler, so your radiators will not feel as warm - this is because they are now more efficient and don't need to be as hot. It will provide gentle heating over longer periods rather than quick boosts of heat on demand.

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What to consider before buying a heat pump

There are a few things to consider before buying a heat pump, such as:

Air source heat pump costs

Prices start from £3,500 in England and Wales or £3,000 in Scotland (including the government grants).

Upgrading radiators for air source heat pumps

Some heat pump system designs, particularly low-temperature heat pumps, may also require larger radiators to work at their maximum efficiency. 

Air source heat pump for underfloor heating

Heat pumps work best when there’s less of a difference between the inside and outside temperatures. Floors cover a much bigger area than radiators, so they don’t need to get as hot to provide the same amount of heat. This makes them a good match for underfloor heating, but it's not essential. 

Heat pumps for water heating

Heat pumps can also be a great source of hot water – but the water is likely to be around 50-55 °C with a heat pump, compared to 60-65 °C with a boiler.  This means that if you’re running a bath, you’ll need more hot water and less from the cold tap. 

Advantages vs disadvantages of a heat pump

Advantages

Disadvantages

  • To improve running costs and qualify for any government support you may need to invest in improving your insulation. Adding more insulation is beneficial regardless of the heating system you have
  • Even with government initiatives, an air source heat pump costs more than other heating systems
  • Installation can take 3 - 8 days and the whole process of buying a heat pump may take around 12 weeks
  • You'll need space - outside for the pump and inside for a water storage tank. Some heat pumps may also need an indoor unit but don't worry, this will replace your existing boiler

Are there different types of air source heat pumps?

Air to water air source heat pumps

In air-to-water heat pumps systems, the heat is transferred into a ‘wet’ heating system (conventional radiator central heating). This set-up gives you hot water and keeps your home warm. Only these heat pumps qualify for the Boiler Upgrade Scheme.

Air to air air source heat pumps

As their name suggests, air-to-air' air source heat pumps transfer heat directly into the air in your rooms. More commonly known as air conditioning units, they can be switched between heat and cooling depending on the season. It's worth noting, these heat pumps don’t provide hot water.

Hybrid' air source heat pumps

These heat pumps are combined with a boiler. Depending on the type of hybrid system, the boiler can assist the heat pump by providing hot water or a quick heat boost during a particularly cold snap.

What are the running costs of an air source heat pump?

Energy prices vary - and our homes and energy use differ too. So it's hard to give an exact figure for how much money it could cost to run a heat pump. But, based on October fuel cost figures, we've put together this example based on a home using 12000 kWh of heat per year.

A 3 bedroom house might need about 12,000kWh of heat per year (although this will vary). We divide the heat requirement by the efficiency of the appliance, then multiply it by the price of the fuel to get the total running costs. Therefore, to heat this particular home at the current average fuel prices: 

  1. A new gas boiler could cost about £899 per year: (12,000kWh ÷ 92%) x 7.5p per kWh of gas    
  2. An older, 70% efficient gas boiler could cost about £1,181 per year: (12,000kWh ÷ 70%) x 6.89p per kWh of gas     
  3. An oil-fueled boiler could cost about £1,043 per year: (12,000kWh ÷ 92%) x 8p per kWh of oil
  4. An LPG-fueled boiler would cost about £1,434 per year: (12,000kWh ÷ 92%) x 11p per kWh of LPG
  5. An air source heat pump would cost about £1,094 per year: (12,000kWh ÷ 300%) x 27.35p per kWh of electricity

Are there any maintenance costs to air source heat pumps?

Air source heat pumps have a working life of 15 years or more. But just like a boiler, you should get your air source heat pump professionally serviced annually to maintain your warranty coverage and to make sure it's still working at its best. There are some things you can do yourself:

  • Make sure that there's plenty of air around your heat pump. This means regularly checking for leaves or rubbish caught at the back and side of the heat pump and pruning back any plants growing too close to the unit or its pipes
  • In very cold weather make sure to clear snow from the air source heat pump
  • Follow your installer's instructions on how to use your heat pump
  • All of our heat pumps come with a manufacturer's warranty of up to 7 years

How to get an air source heat pump

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