Air source heat pumps explained

02 July 2020 | OVO Energy

Scientists and inventors are constantly trying to come up with greener ways to heat our homes. Boilers are getting more energy efficient almost every year – but they’re no longer necessarily the best way to run a central heating system.

Air source heat pumps have moved the goalposts. They’re super low carbon and low maintenance, and they could cut your home heating costs. But are they right for your home? Let's have a look first at what an air source heat pump is.

What is an air source heat pump?

Air source heat pumps are a way to heat your home that could give you a greener alternative to boiler heating systems. They’re low maintenance – and they might just cut your heating costs. Win win.

Air source heat pumps use air as their main source of energy. They take energy from the air outside (even when it’s super cold) and convert it into heat for your home. Basically, they work in the same way that fridges and air-conditioning units do, just in reverse. 

How air source heat pumps work

Get your science hat on and let’s look at the process in simplified steps:

  • The unit absorbs heat from the air into a liquid refrigerant 
  • This fluid is turned into gas in the process 
  • Using electricity, the pump compresses this gas, heating it up 
  • This heat is transferred into your home’s heating system – your radiators, underfloor heating, or warm air convectors and hot water
  • Lastly, as the heat transfers, the gas condenses back into a liquid and the cycle begins again
How air source heat pumps work

A compressor unit is fitted outside of your home. It’s useful to have a sunny spot for this so the pump won’t have to work as hard. But it can even absorb heat from the air at sub-zero temperatures – so it’ll work even if you’ve only got a shady space.

Benefits and disadvantages of air source heat pumps 

They’re low maintenance and are generally more environmentally friendly than the systems they replace. The main component used to create heat is air – a natural, renewable resource. But they’re not suitable for all types of home, and it’s good to be aware of the pros and cons:

Pros of air source heat pumps

  • They could lower the costs of heating your home – if you’re switching from an electric, oil, LPG (liquefied petroleum gas) or coal-fuelled system
  • They produce fewer carbon emissions than most boiler systems 
  • Using air, a renewable resource, means they’ll help lower your carbon footprint – by how much depends on the fuel source they replace
  • They’re very efficient – they run well without wasting much energy
  • They typically last longer than a boiler – about 20 years

Cons of air source heat pumps

  • The pump works best for lower heating temperatures – so they’re ideal for large radiators or underfloor heating
  • They provide a lower temperature than traditional systems (so insulation and draught proofing helps with heating efficiency, to keep your home toasty too)
  • Only homes with outside space can get one of these systems – but they could free up space inside where your boiler would be
  • Some (usually older) models can have rather noisy outdoor fans. Although manufacturers are working on new ways to keep noise low – some are even quiet.

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There are two types of air source heat pumps

Air-to-water systems distribute heat by pumping liquid through pipes and radiators, or through underfloor heating pipes. Right now, this is the most common type, as it can be used for heating and hot water.

Air-to-air systems produce warm air, which is circulated around your home by a network of fans. 

What makes air source heat pumps super low carbon

Air is the main thing that these pumps use to create heat. And that’s a renewable resource, if there ever was one.

But, the unit does use some electricity to run, so it isn’t completely carbon neutral. It uses electricity more efficiently than regular electric heating units and is generally more environmentally-friendly than most heating systems. 

The costs of air source heat pumps

Installation costs

Fitting a typical air source heat pump could cost between £9,000 and £11,000, according to the Energy Saving Trust. The exact cost depends on the size of your home and your insulation. Always make sure you get several quotes and go with a trusted installer.

Running costs

The running costs will depend on:

  1. The size of the home – the bigger the space, the more power needed to heat it 
  2. How well insulated it is – better insulation means less heat loss
  3. How warm you want it to be

  4. Whether you have underfloor heating or radiators

Air source heat pump savings 

air source heat pump savings

Any savings you make will depend on what kind of fuel you’re replacing. If it’s gas, your gas use will go down and your electricity will go up. It could take many years to recoup the costs of installing one.

However, it could work out cheaper than an electric, oil, LPG or coal system – particularly an old, inefficient one.

Air source heat pumps could be the best option if you’re building a new home. They’re comparatively simple to install and you can include underfloor heating at the same time. You could also add solar panels to provide hot water in the summer, which would make it easier for the pump to heat up your home.

Things to consider before installing an air source heat pump

Air source heat pumps work best with a well insulated home. 

Here are some good ways to insulate your home:

Other things to think about before you go for it:

  • You’ll need the units to be installed outside your home against a wall, with good airflow
  • How quickly you could make savings with an air source heat pump, depends on the energy source you already use. If it’s coal or electricity, then switching will be more efficient – saving energy and money. 

Financial help towards installing an air source heat pump

Your home might just qualify for help through the domestic Renewable Heat Incentive (RHI) scheme in the form of a grant. Find out more about the scheme on our blog. This is due to end in March 2022 and be replaced with a new scheme, the Clean Heat Grant

To help the UK reach its target of net zero emissions by 2050, this government scheme helps support people who have certain renewable technologies in their homes. It provides quarterly payments for 7 years, meant to offset the cost of fitting and running your renewable heating system. 

To find out more about these schemes, get in touch with the Energy Saving Advice Service on 0300 123 1234 if you live in England or Wales, or Home Energy Scotland on 0808 808 2282 if you’re based in Scotland. (Visit to see how much the call might cost you.)

Air source heat pump energy labels 

All air source heat pumps fitted today have to have energy labels on them, providing information about efficiency. They’re rated with a colour code system – dark green means most efficient and red is least.

Other ways to cut energy costs

Installing an air source heat pump can make a big difference to your carbon footprint, but they can also be expensive – so you might want to find other ways to save on your energy bills. To start with, make sure your home and all your electrical appliances are working as efficiently as possible. 

Here are some more suggestions:

  • Turn appliances off at the wall – don’t leave them on standby
  • Use energy-saving light bulbs and other energy-saving devices 
  • Insulate your hot water tank – you could save around £35 a year
  • When using your washing machine, set it at 30˚

Then check out 120 ways to save and conserve energy.

It also makes sense to consider switching providers. No matter which energy company you’re currently with, it’s always worth checking the market regularly to see if you could save money by switching.

At OVO, we know that price matters – that’s why we keep our costs down, to help you save. You'll also get our 3% OVO Interest Reward answers on any credit in your account.

See how your current provider matches up next to our range of energy plans – you can compare energy prices for our electricity, gas and dual fuel plans. They’re based on a medium user, paying by Direct Debit, averaged across all UK regions. It’s the quick and easy way to compare utility prices.

Our Zero Carbon Heating Trial

Why not check out our Zero Carbon Heating Trial? We'll be installing up to £15,000 worth of technology (including air source heat pumps) in 250 households in South East England.

Find out more


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