How do they work, what do they cost and are they noisy?

The government’s Warm Homes Plan promises £15bn to help UK households pay for green technologies such as heat pumps, as part of its efforts to drive down energy bills and cut planet warming emissions.

Heating homes accounts for about a fifth of the UK’s planet-warming emissions, so switching from gas and oil to heat pumps is seen as a priority.

Heat pumps run on electricity instead of gas. They warm buildings by absorbing and amplifying heat from the air, ground, or water.

They are widely seen as the best way of cutting emissions of carbon dioxide and helping to achieve net zero goals.

Heat pumps are more efficient than gas boilers. They can use electricity generated from increasingly clean sources, as wind and solar power replace polluting fossil fuels.

Air source heat pumps – the most common type – suck in outdoor air and pass it over tubes containing refrigerant fluids. The heat from the outdoor air cause the refrigerants to evaporate into a gas, which is then compressed causing its temperature to rise, and the heat is passed round the home.

The system consists of a box measuring about 1m x 1m x 0.4m which stands outside the property, as well as a heat pump unit and hot water cylinder inside the property.

The indoor unit is about the size of a gas boiler, while the cylinder depends on the size of the home.

Ground source heat pumps are more efficient than air-source models.

However, they are typically more expensive and less commonly used, as they require either a deep bore hole or a horizontal system dug into the ground over a large area.

The Boiler Upgrade Scheme provides a grant of £7,500 towards an air source or ground source heat pump, for homeowners in England and Wales.

With the grant, households spend an additional £5,000 on average, which the UK’s spending watchdog has warned is too high for many.

The grant can be used for existing homes and non-domestic buildings. The property must have an eligible Energy Performance Certificate (EPC), issued in the last 10 years.

The government’s latest Warm Homes Plan has extended this scheme to 2029/30.

Changes to the rules mean homes are no longer required to have existing loft or cavity wall insulation, which could save around £2,500 in upfront costs. A well-insulated home can help a heat pump perform more efficiently.

For low-income households and those in social housing, the government is extending £5bn funding for the Social Housing Fund and the Warm Homes Local Grant.

The Warm Homes Local Grant offers funding for insulation, solar panels and air source heat pump via your Local Authority.

You must be in England, privately own or rent your property and have an energy performance certificate (EPC) – a measure of energy efficiency – of between D and G.

Scotland, and Northern Ireland, have separate schemes to help make homes more efficient but the plan is issuing more funds to these devolved programmes.

While the upfront costs remain substantial, heat pumps could become cheaper to run than gas boilers, according to the Climate Change Committee (CCC), which advises the UK government on cutting emissions.

The cost depends on energy prices and how efficiently the heat pump works.

Electric heat pumps use much less energy than gas boilers, but electricity typically costs more than gas.

Energy deals designed for heat pump owners can help households make savings and install solar panels, which means they can generate their own energy rather than rely on the grid.

Nesta, the social charity, have estimated that with solar panels and a heat pump the average home could save nearly £1,000 on its energy bills annually.

Previously, homeowners needed planning permission if they wanted to put a heat pump within one metre of their neighbour’s property, because of concerns over noise.

The rule was dropped to accelerate the uptake of heat pumps.

Concerns over noise are also less of an issue with newer devices, though units will still be required to be below a certain volume level. This has been set at 42db, which is a similar output to that of a fridge.

The rules for the size and number of heat pumps households can install have also been relaxed.

The plan includes the Warm Homes Fund, which aims to offer low-interest and zero-interest loans for solar panels and domestic storage batteries for all households.

The government has not yet decided when or how households can access these funds, but said it would announce further details later this year.

Those on low-income will be able to get the technologies covered as part of the existing Social Housing Fund and Local Grant.