Air Source Heat Pumps


Taking heat from the air and putting it in your home.




An air source heat pump is a renewable heating system that absorbs heat from the air around your property and uses it to heat your hot water and central heating system.

How do air source heat pumps work?

Air source heat pumps work on the same basis as air conditioning units or refrigerators, but in reverse. An air source heat pump system sits outside the property, in a position that allows for a steady flow of air.

Large fans on the air source heat pump unit draw air in, passing it over a heat exchanger that sits directly behind the large fan. Through the heat exchanger flows a liquid refrigerant, which functions at temperatures far below 0oC. As the ambient temperature stored in the air comes into contact with the heat exchanger, the liquid refrigerant heats up.

The warmed up refrigerant is passed to a compressor where it is condensed. Its temperature is raised further, to a point where it is ready for distribution around the central heating system of a home.

The most common setup with an air source heat pump system is to install a buffer tank inside the home. The buffer tank stores hot water, warmed directly by the heat pump. The water in the buffer tank is used around the home’s central heating system, heating up radiators and underfloor heating. The cold water from the central heating system is then fed back into the buffer tank to be re-heated, creating one continuous loop.

Typically, a separate hot water tank will also be installed in the property. The hot water tank is separate to the buffer tank but is also heated by the air source heat pump. A hot water tank is used to provide instant hot water for the home.


What advantages are there to installing an air source heat pump?

An air source heat pump system is an entirely renewable form of heating. It’s a system that is free from burning fossil fuels, and this brings huge advantages over gas or oil-fuelled heating systems:

  • Zero carbon emissions produced from your home. 
  • A far more efficient heating system – an air source heat pump system can return a coefficient of performance rating (CoP) of 3 or above. For every 1kW of electrical energy used to power the air source heat pump, 3kW of heat energy is returned.
  • Safer than fossil fuel-burning systems. An air source heat pump system is powered entirely by electricity. They emit zero air pollutants and are combustion-free.
  • Air source heat pumps are a perfect complement to other renewable systems: underfloor heating and solar panels.
  • Government incentives are available to homeowners and businesses, funding the installation cost of an air source heat pump.
  • Air source heat pumps are relatively easy to install and require very little ongoing maintenance.
  • No fuel deliveries needed.

How much does an air source heat pump cost to install?

The installation cost of an air source heat pump varies from property to property. An air source heat pump system must be designed correctly by a qualified engineer. It must be correctly measured and sized to ensure it works efficiently and is cost-effective for your home.

There are a lot of different variables that need to be considered to ensure the air source heat pump system being installed in a home will work efficiently and be a cost-effective solution.

The following factors will determine the cost of an air source heat pump system:

  • The size of the property
  • The materials used to build the property
  • How well insulated the property is

A typical air source heat pump system installation cost ranges between £10,000 and £16,000. For an accurate quote, it’s recommended you contact Thermal Earth directly so that we can organise a site visit. That way, we can learn more about your property, your needs and preferences, and then tailor a system that works perfectly for you.

How much does an air source heat pump cost to run?

Air source heat pumps that have been thoughtfully designed and installed tend to be cheaper to run than fossil fuel-burning boilers. In the right set up, a correctly sized air source heat pump will provide three times the efficiency of a gas boiler, and this can lead to savings on energy bills in the long term.

There are different factors that will affect how efficient an air source heat pump is, and these will have a bearing over how much it costs to run. Those are the heat demand of the property and the efficiency of the heat pump.

Heat demand

The heat demand of the property is determined by how warm you want your home and the temperature of the hot water. The higher the temperature; the greater the heat demand; the higher the running costs.

Efficiency of the heat pump

How much electricity it takes to provide heating and hot water determines how efficient a heat pump is. The more electricity the heat pump has to use to get your home up to temperature, the less efficient it is.

A more efficient heat pump generally means that it won’t have to work as hard to provide the heat needed. It’ll keep power consumption to a minimum and cause less wear and tear on its components. This will reflect in lower running and maintenance cost for the homeowner.

But there isn’t a one-size-fits-all approach to judging how efficient an air source heat pump will perform. It is dependent on the characteristics of the home the heat pump is being installed in. These characteristics include:

  • Where on the property the air source heat pump is located.
  • How well insulated the property is.
  • The brand of heat pump installed.
  • Using the heat pump in a way that is economical.

Coefficient of Performance

The efficiency of a heat pump is measured in Coefficient of Performance (CoP). On average, an air source heat pump has a CoP of 3 – 4. What this means is that for every 1kW of electrical energy used to run the heat pump, the system will provide 3 - 4kW of heat energy.

In comparison a fossil fuel boiler will provide an average CoP rating of 0.8 – 1, making an air source heat pump approximately 300% more efficient.

Renewable Heat Incentive

Installing an air source heat pump is really beneficial, both to property owners and to the environment. But the initial cost of installing a system can be expensive.

To make sure people aren’t deterred from embracing low-carbon heating, the UK government offers grants to help fund the cost of an air source heat pump system.

The scheme is called the Renewable Heat Incentive (RHI) is offered to two different stakeholders:

  • Domestic RHI: Aimed at current home owners and private or social landlords, domestic RHI is paid out over the course of 7 years and is based on the amount of heat produced by a renewable heating system.
  • Non-Domestic RHI: Aimed at public sector organisations, private businesses and housing developers, the non-domestic RHI pays applicants over the course of 20 years.

Added to this, homeowners can also get the cost of the installation funded through the Assignment of Rights programme. An option under the Domestic RHI scheme which allows homeowners to nominate an investor to cover the installation costs in return for the rights to claim the RHI repayments.

Is an air source heat pump right for you?

To understand whether an air source heat pump would be right for your property, there are a couple of thoughts to take into consideration:


Do you have the available space at your home to place an air source heat pump? To get the performance from the unit, it should be placed in an open space with good airflow around the unit.

If you have ample space available at your property, you may want to consider a ground source heat pump as an option instead. They cost slightly more than an air source heat pump but the benefits in terms of efficiency and stability can provide even greater results in the long term.

Current system being replaced

Air source heat pumps are best suited to those homes that are replacing old, inefficient heating systems or those homes that are off grid. Replacing a G-rated gas, oil or LPG boiler could see you save as much as £1,000 a year on your annual bills according to the Energy Saving Trust.

Side-to-side with a brand new A-rated gas boiler, the cost of running an air source heat pump is so similar as to not make much difference to your heating bills. Space allowing, we’d recommend looking to an even more efficient ground source heat pump in this instance.


How well insulated is your property? Air source heat pumps are designed to work at low temperatures. They react best and achieve the best performance in homes that are draught-free and retain heat well.

Heating system

As air source heat pumps work at lower temperatures, they are best suited to underfloor heating or low-temperature radiators. This is not to say these are necessary for an air source heat pump to work, but they will aid its efficiency. 

MasterTherm Air Source Heat Pumps

Thermal Earth is the UK-exclusive distributor of MasterTherm heat pumps. The Czech company is a giant in the renewable heating industry, leading the way on heat pump technology for 25 years.

MasterTherm supply a wide range of air source and ground source heat pumps. One of the most popular units in the line-up is their air source heat pump, the BoxAir Inverter.

The BoxAir Inverter, as its name suggests, is a heat pump that features Inverter drive technology. The BoxAir heat pump reacts to the changing heat demand of the property and adjusts its output. Generally, it needs less power consumption and extends the lifespan of the heat pump. You can find out more about Inverter heat pumps in our blog.

MasterTherm’s air source heat pumps offer distinct advantages compared to its competitors.

  • Online functionality
  • 7-year warranty
  • Ultra quiet
  • Increased efficiency with Inverter technology

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