Air Source Heat Pumps

Air source heat pumps are an exceptionally clean and efficient source of producing heating and hot water for domestic properties and commercial sites.

An air source heat pump works by extracting readily available heat in the air and local environment through temperatures between -20^oC and +35^oC, which helps to reduce the dependency on fossil fuels as well as significantly cutting carbon emissions. Air source heat pumps use electricity to operate and run the heat pump. For every 1kW of electricity used, between 3kW and 4kW of thermal energy is available for heating and hot water is available.

How does it work?

An air source heat pump works by extracting energy from the surrounding air. It does this by running a fan which pulls relatively warm air across a very cold heat exchanger. Energy is transferred into the gaseous refridgerant inside the heat exchanger, which then flows into an electrically driven compressor. This gas is then compressed, generating the high grade heat needed to provide heating and hot water for your home.

With this technology a correctly sized air source heat pump can work down to around -15^oC ambient air temperature which is more than sufficient for mid-winter UK temperatures.

What do I need to install it?

A small concrete base with a drain or soak away will need to be constructed outside in an area where the unit will not cause too much disruption. The noise output of the unit up close is relatively quiet (similar to that of a dishwasher in the next room) however it should still be located in a sensible location, for example on an unbroken wall near a utility room where it will not disturb the occupants of the property. The outside unit can be sheltered by coniferous plants or slatted timbers if it needs to be hidden from view.  A 1m² space will be required for a new hot water cylinder inside the property.

The key to installing heat pumps of any kind is that the heating emitter circuit is optimised to work with heat pumps and run at lower flow temperatures (around 40^oC-50^oC) than used with a conventional fossil fuel boiler. This means the compressor will have less work to do to convert the low grade heat extracted from the ground into high grade heat needed for heating. The installation as a whole will therefore use less electricity, increasing efficiency and decreasing running costs.

With a modern property and underfloor heating, lower flow temperatures are easy to ensure. Underfloor heating on either solid or joisted floors can be designed to run at temperatures even below 40^oC in certain properties (we offer a full in-house design and installation package for Underfloor Heating – Please Click here for more details) and low flow temperature radiators can be built in if required.

In a domestic retrofit environment we will undertake a careful assessment of the existing radiators. Often radiators were designed using the Mears formula, which significantly oversized the emitters to ensure that rooms could be brought up to temperature quickly when the boiler fired. This oversizing often matches the heat pumps requirements, so generally only the radiators in rooms that are already cold with the existing heating system need up-sizing whilst the rest will work with a heat pump system.

How much will it save me?

A well installed heat pump should run at a Seasonal Coefficient of Performance (SCOP) of around 3:1 to 4.5:1 on average throughout the year, depending on the flow temperature of the system between 35degC and 55degC. This means that for every 1kWh of electricity needed to run the compressor 3kWh of heat will be generated by the heat pump.  At an electricity cost of 28p/kWh (as per the April 2022 Ofgem Price Cap) therefore a heat pump will cost around 7-9p/kWh to run.

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