Heat pumps: How do they work and how do I get one?

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Engineer inspecting heat pumpImage source, Alamy

From Monday homeowners can apply for a government grant of £5,000 to replace their gas boilers with heat pumps.

This is part of the government's efforts to reduce carbon dioxide - a greenhouse gas responsible for climate change.

What is the scheme and who is eligible?

The boiler upgrade scheme was announced in 2021 to help reduce the cost of more environmentally-friendly heating systems.

Grants will be available to existing homes and non-domestic buildings in England and Wales.

They can be used for the following four systems up to 45kW in size (the average home in the UK requires a 4kW system):

  • air source heat pump
  • ground source heat pump
  • water source heat pump
  • biomass boilers (for those living in rural areas)

The property must have an eligible Energy Performance Certificate (EPC) issued in the last 10 years, and the certificate must have no outstanding recommendations to install loft or cavity wall insulation.

If it does, you'll need to insulate your home first, or as part of the application process.

The scheme will not be available if you live in social housing or a new-build property. Private rented accommodation is also eligible but the decision has to be taken by the landlord.

Image source, Getty Images
Image caption,
Air source heat pumps sit on the outside of the house

What will the government pay for?

The government is providing £5,000 for households to install air source heat pumps (ASHPs) - which would cover between 75% and 50% of the cost.

It will provide £6,000 for the less commonly used ground source heat pump (GSHP) or water-source heat pump (WSHP). This would cover between 50% and 30% of the cost of the unit, although the cost of installation (digging a hole, for instance) could be significantly higher.

The government has set aside £450m for this scheme, which will cover a maximum of 90,000 boilers.

Chancellor Rishi Sunak also announced in his Spring Statement that there would be no VAT on heat pumps for five years in England, Scotland and Wales.

How do I get a voucher?

The first step is to contact an MSC-certified installer, of which there are 773 in the UK. Search for one local to you using this tool.

Once they have provided a quote, the installer will then apply for a voucher from the Office of Gas and Electricity Markets (Ofgem), which is managing the scheme.

If Ofgem approves the voucher, it will send a direct payment to the installer after the work is completed. The householder will then pay the remaining balance.

Installation must be completed within three months of the voucher being approved for an ASHP, or six months for a GSHP.

The scheme is expected to run for three years until 31 March 2025, and it is operating on a first-come, first-served basis.

Will it be cheaper to run than a gas boiler?

Heat pumps are normally three times more efficient than gas boilers but they use electricity to run, and electricity prices are typically more expensive than gas.

However, given the current high price of gas, heat pumps could still be cheaper.

The government says it will look at measures to ensure heat pumps are no more expensive to run than a gas boiler in the long run.

How does a heat pump work?

A heat pump is an electrically powered device that absorbs heat from the air, ground or water around a building.

For example, air-source pumps suck in outdoor air and pass it over tubes containing refrigerant fluids to produce heat.

Media caption,

Heat pumps explained in 60 seconds

How much room does a heat pump take up?

A box of about 1m x 1m needs to stand outside - close to, or attached to the property - to draw in air.

It should be at least 1m from your neighbour's property so they will not be able to hear it, although it won't be much louder than a fridge.

You will also need space inside for a heat pump unit and hot water cylinder. The unit will be about the size of a gas boiler - while the cylinder depends on the size of the home.

A ground source heat pump needs much more space outside - either a bore hole as deep as 100m, or a horizontal system dug into the ground over a large area.