How do air source heat pumps work – a case study

Everything you need to know about air source heat pumps – and our case study

a before image of the back of a house
after picture of a house with a new air source heat pump and new windows and doors

An air source heat pump that we fitted in summer 2022. (This customer also required new windows and doors to qualify as part of the Home Upgrade Grant in Cheshire). Scroll down or click here to jump to the full story!

What is an air source heat pump?

Heat pumps are a low carbon heating technology. They can replace your boiler or electric heating. You will still use radiators. Only some types can provide your home with hot water. Most air source heat pumps are around the same size as a washing machine, and they must be installed outside. They use electricity to move heat from outside air to heat the inside of a property. They function even in below freezing temperatures.

an air source heat pump outside in a garden on a sunny day

How do air source heat pumps work?

ASHPs use the same technology that keeps the inside of your fridge cold, but in reverse.

an air source heat pump works similarly like refrigerator. During the heating season it heat from outside to inside and the opposite is true during the summer months. A heat pump actually moves heat rather than generates heat

  1. A liquid is pumped on a loop between two heat exchangers. This liquid takes on heat energy from the outside air temperature and turns into a gas as it warms up. (There is always some heat energy outside).

  2. This gas is then compressed back into a liquid. The warm liquid then goes through a heat exchanger, which transfers the warmth to a separate body of water for circulating around your central heating system.

  3. This cycle repeats.

The UK needs to upgrade from gas boilers fast to make an impact on the climate crisis. According to Octopus Energy, air source heat pumps are “the most carbon friendly solution out there, and with global gas shortages pushing gas prices up to a 16 year high, heat pumps are now the cheapest option to warm your home.”

Does an air source heat pump work in winter?

The process is very efficient, as they can deliver around three to five units of heat for each unit of electricity needed to run them. Heat pumps do not rely on fossil fuels. 

air source heat pump unit on the side of a home in winter.

Air source heat pump cost

The cost of an air source heat pump in the UK, on average, is about £8,000. However, there are multiple government funding schemes available to make the install completely free or reduce it substantially.

What grants are available for air source heat pumps?

If you qualify for the ECO scheme, your install will be completely free.

There is another government scheme currently operating which can get applicable households £5,000 off. The Boiler Upgrade Scheme is suitable for many people across England and Wales. It does not matter if you own or rent your home. All applicants must have a valid EPC rating. On the Energy Performance Certificate, there must be no recommendations for loft insulation or cavity wall insulation. If there are, then you must have the insulation installed before applying. (Luckily, loft insulation is pretty cheap and you can do this yourself.) If you do qualify, the remaining sum of £2000 is around the price of an average boiler upgrade. 

Get in touch with us or your local council to see if there is any applicable funding for your household to get an air source heat pump funded. There may be other grant schemes available, such as ECO Flex or ECO+.

Is an air source heat pump worth it?

Despite any negative press about air source heat pumps, this has not stopped other countries from installing thousands of them.

The UK is far behind other countries in terms of ASHP installs. Several sources have pointed out how many other European countries have much higher rates of air source heat pumps. China is the world leader for heat pump adoption.

America and Canada are also beating us. There are currently more heat pumps in colder countries than anywhere else in the world, which shows that they definitely do work in colder climates!

Are air source heat pumps expensive to run? 

The cost to run a heat pump can depend from house to house. It will change based on the size of your home, its insulation, and how much heating you use.

Octopus Energy found that on average a heat pump costs £187 less a year to run than a boiler. ASHPs also have a longer lifespan than gas boilers.

Air source heat pump disadvantages

  • If you can’t qualify for government funding or afford a heat pump easily, the upfront cost is unavoidably the biggest downside. As they become more common, their price point is sure to become more affordable.
  • The heat pump will emit cold air outside. If it is placed next to a barbeque or garden furniture this could be unpleasant.
  • They do use some level of electricity which will add a bit to your electricity bill (though you will have no gas bill whatsoever).
  • Some people have reported that air source heating systems do not generate as much heat as boilers. If you have a very large house, you would notice this the most. In this situation you might need larger radiators or additional radiators in large rooms. This should solve the issue and if you qualify for a grant you would also qualify for improved, more suitable radiators.

Are air source heat pumps noisy?

ASHPs are as loud as air conditioners or electrical fans. The UK government has reported that air source heat pumps are as loud as gas boilers.

Can air source heat pumps cool? 

Some types of heat pump can. Air to air heat pumps can give out air con, but most air to water heat pumps (which is what we fit) can’t. Air to water heat pumps are amongst the most efficient air source heat pumps on the market. The reason we fit these is because they function the best in climates of around 7°C and below. These are the most common type installed on the retrofit market but they are suited to new builds too!

Traditionally, air to water heat pumps could not provide both heating and cooling, but there are some on the market now which can. Reversible heat pumps work in either way to provide both options for your property. 

Is an air source heat pump suitable for my home?

If you live in a flat, it will be more difficult to have a heat pump installed. Though it is possible to install a heat pump on a balcony or outside area if you have access to one, this will in general be more complicated than if you lived in a house.

In 2020, the government produced the Electrification of Heat Demonstration Project. It aimed to prove the feasibility of a large scale roll-out of heat pumps in Great Britain by installing heat pumps in different types of home. 742 homes had the install. Great Britain has diverse housing stock and there were some doubts that not every home would be suitable, but the findings of the project proved otherwise!

Several different energy companies were involved in the mass installation, such as E.ON and OVO. The project focused on three different regions: Newcastle, South East Scotland, and South East England. The project was successful in many different types of home: from flats to houses of any attachment type. It was also successful in older homes as well as new builds. 163 heat pumps were installed in homes built prior to 1945, though there were greater challenges involved here.

loft insulation being installed

However, even with these positive findings, there is a major factor which would help your property to be more suited to an air source heat pump, and this is insulation.

Your property should be well insulated in order for an air source heat pump to work most efficiently. Insulating more of your home is a good choice no matter what your heating source, because insulation will always make you less likely to turn your heating on as your home will already feel warmer. If your heat pump, or any heating source, had to work less hard to up the temperature of your home you would also save on your energy bills.

February 2023 – Octopus Energy launch competitively priced heat pump

During an interview with The Telegraph, Octopus CEO Greg Jackson stated that their own air source heat pumps can now be installed at a similar price to gas boilers.  This is only after the customer has applied for a government grant for the heat pump: the Boiler Upgrade Scheme.

Air source heat pump installation 

Install orders can change from property to property, but first an installer will always come out to undertake a survey of your home and map out how the new system will fit. You most likely will not have access to heating while the installation is taking place but you could be left with hot water every evening. If you have a gas boiler, this will be removed. You might have a new hot water tank installed.

The rest of the install will involve plumbing, new pipe work, and install of the heat pump outside. The indoor control unit will be installed. This will be linked up to your central heating and the heat pump outside. If you have very large rooms, you might need new, bigger radiators installed too. The install time takes about 2 to 5 days on average.

air source heat pump installation

After install

After install, there is not much maintenance. Your installer should explain how to change any settings you might need to. A lot of the maintenance is visual. You will need to check the outdoor unit has no leaves or dirt blocking it from working. Most workmanship warranties last about 10 years. Some installers may require the system to be serviced annually to ensure the warranty is valid.

Customer journey of getting a heat pump

This government document displays the typical process of getting an air source heat pump, from the customer enquiry stage, survey and design stage, installation stage, and post installation stage. This document shows conversations you will have with an installer every step of the way.

Air source heat pump: our case study

The problem

a before pic of a house before an air source heat pump install
Before picture – Sandbach, Cheshire

Our customers lived in a 70 year old 3 bedroom end terrace house. They had an old fashioned back boiler as their heating system. The current heating system was costing a lot of money and had poor efficiency. The back boiler needed updating as it was over twenty years old and the customers wanted a solution that would increase the value of their house whilst allowing them to be more environmentally aware.

The property was large and old with an above average sized roof. The clients had no loft insulation, very old radiators, and old fashioned single glazing.

The solution

an air source heat pump at the back of a property
After picture – We fitted an air source heat pump, new windows and doors, and solar panels

We fitted an air source heat pump as they had more than enough room in their back garden, but as you can see from the photo above, heat pumps aren’t very large and would be suited to much smaller outdoor spaces too. The heat pump automatically sets the level of inside heating by adjusting to the outside air temperature. The client found the system easy to use, they had noted the consistent temperature, and found it keeps the home consistently warm and comfortable!

On the Home Upgrade Grant at the time in Cheshire, this customer also qualified for solar panels, new radiators, and new double glazed windows and doors.


Customer testimonial:

“I applied for the Home Upgrade Grant through Cheshire East council. After a seamless experience with them, I was introduced to Improveasy who were responsible for surveying and installing.

Everything went without a worry. I had a survey done straight away and it was explained that to make my home more energy efficient, I was going to have an air source heat pump fitted, solar panels on my roof to help run the cost of the heat pump and generally save money on my electricity bills, loft insulation fitted, and double glazing throughout.

No catches. All totally free under the Home Upgrade scheme. I made a small contribution to have windows to my own colour choice and some new patio doors.”

heat pump
large radiator with a trv

“I was left all the relevant brochures to understand what they had fitted and how it all works. Now, weeks later, I am noticing the change in my costs, because the solar panels help save on my electricity usage and the heat pump is saving me on previous old heating bills.”

solar panels fitted onto a roof
Solar panels fitted onto the customer’s roof

“The work finished on time, my house was left spotless, and the lads were immaculate in their manners and their communication. I now have all the numbers I need to ring through and ask for advice or to refer a friend. Perfect service!

If only Martins Money Tips would highlight the grants available to homeowners!”

air source heat pump figures before and after install regarding co2 emissions

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