All you need to know about ground source and air source heat pumps

Advice on ground source and air source heat pumps from how they work to cost and suitability

We asked Chris Delaney, Director of Yorkshire-based Green Building Renewables, to give us the low down on heat pumps, how much they cost and why they matter. Here is what he said:

Why heat pumps? As the National Grid is increasingly generating power from renewable energy, heat pumps can offer an energy efficient and low carbon method of heating your home.

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Heat pumps also often work well with solar photo voltaic, aka electricity generating solar PV, and battery storage, enabling greater energy independence and helping future-proof homes.

Advice on heat pumps

As well as reducing carbon emissions, heat pumps can also potentially offer a cheaper form of energy for homes in rural areas that are off mains gas grid and rely on stored oil or LPG for heating.

How do heat pumps work? Air source and ground source heat pumps absorb heat from the outside ground or air and convert that into heat and hot water for your home. Heat pumps use reverse refrigeration technology to deliver an energy multiplier effect. The efficiency of how the heat pump converts electricity to heat using the refrigeration process is called the Coefficient of Performance (CoP). For example, if a heat pump system has a CoP of three, then for every 1kWh of electricity used to run the system you will potentially get 3kWh of energy for heating. Typical CoPs for air source heat pumps are around 3.5 and for ground source heat pumps CoPs are around 4.5.

Ground or air source? There are two main types of heat pump available: Ground source heat pumps rely on absorbing the heat from under the ground using cables that are buried one metre underground in 50 to 100 metre lengths.

Ground source heat pumps are more efficient and have a greater CoP than air source systems as the temperature of the ground is fairly constant.

However, ground source pumps do require a large outside space for all the pipework, the equivalent of half a football pitch. Typical system costs are £20,000 to £25,000.

Air source heat pumps involve a small-sized unit being located outside close to the building. Air source heat pumps are not as efficient as ground source in terms of converting electricity to heat but they are about half the price and do not require a huge amount of outdoor space. Typical system costs are £10,000 to £12,000.

Things to consider: At present, the running costs of a heat pump are roughly on a par with heating your home with mains gas. However, if you are off grid and replacing LPG or oil-fired heating, heat pumps are almost always cheaper to run.

Heat pumps aren’t always suitable for every property. For a larger uninsulated property, the heating demand could be so high in winter that the lower temperature heat pump system would need unfeasibly large radiators to keep the space warm. In such a case, we would recommend insulation and airtightness measures before installing a heat pump.

Financial support: The Government’s s Renewable Heat Incentive (RHI) scheme is due to end in March 2022. It works by making payments to householders over a number of years ranging from between £6,000 – £10,000, depending on the amount of renewable heat generated.

The RHI will be replaced by a new Government grant scheme starting in April 2022 which offers homeowners upfront payments of £5,000 for air source and £6,000 for ground source pumps. The grant will not cover all installation costs.