How does a heat pump work? What are air and ground source pumps, home installation cost and UK grant explained

Households are being encouraged to replace gas boilers with low carbon heat pumps.

The UK government has announced grants of £5,000 will be available to those families ready to make the switch, in a bid to reduce emissions.

Ministers want all new heating system installations to be low carbon by 2035, but the phase out of existing fossil fuel boilers won’t be enforced by a ‘green police’.

Writing in The Sun, prime minister Boris Johnson said: “While we’re going to have to make some pretty major changes to the way we heat our homes, the Greenshirts of the Boiler Police are not going to kick in your door with their sandal-clad feet and seize, at carrot-point, your trusty old combi.”

Here’s all you need to know about heat pumps - from what they are, how they work, and the cost of installation, as well as details about how to apply for the government grant.

What are heat pumps?

The grants are designed to make the installation of heat pumps more affordable so that it made sense to install one when the current boiler needed replacing.

The government’s announcement comes on the eve of COP26, in Glasgow, and against the backdrop of its intention to reach net zero carbon emissions by 2050.

To do that, they need people to change the way homes and buildings are heated.

Heat pumps offer an alternative to traditional heating systems that use fossil fuels and have two types - air source and ground source.

Heat pumps are seen as a low carbon source of heating and more sustainable in the long term.

How do heat pumps work?

Heat pumps work by absorbing heat from source, typically the air or the ground.

The pump transfers heat to a fluid, which is compressed to increase the temperature further, and from there to water which is then used for heating and hot water.

In order to install a heat pump, there are things to consider such as cost and space.

Ground source heat pumps require a garden or outdoor space to install a pipe below ground, whereas air source heat pumps need a good flow of air around them.

Due to the size of work involved, it is recommended to check if planning permission is required.

The pumps work best when producing heat at a lower temperature more frequently, so a well insulated house with little draught will provide better results.

How much do heat pumps cost?

The total cost of having a heat pump installed in your home is thought to range from £9,000 to £11,000 for an air source heat pump and up to £19,000 for a ground source heat pump.

The estimations come from the Energy Saving Trust which say the up front cost is dependent on the amount of heat required for your home.

The organisation also warns households that fuel bills will still need to be paid because the heat pumps are powered by electricity.

Due to green levies higher on electricity than on gas, heat pumps do not necessarily deliver savings on running costs despite being much more efficient than gas boilers.

How can I apply for a £5,000 government grant?

The government’s scheme, which will see £450 million available over three years, will be open to applications from April 2022.

Experts say the pot of money will only be enough to replace 90,000 boilers over the three years, despite making heat pumps more affordable.

Environmental campaigners at Greenpeace and Friends of the Earth criticised the level of funding for heat pumps and energy efficiency measures in homes, while shadow business secretary Ed Miliband labelled the plans a “meagre, unambitious and wholly inadequate response”.

Rolling out low carbon heating will support up to 240,000 jobs across the UK by 2035, ministers said.

Business and energy secretary Kwasi Kwarteng added: “Recent volatile global gas prices have highlighted the need to double down on our efforts to reduce Britain’s reliance on fossil fuels and move away from gas boilers over the coming decade to protect consumers in the long term.

“As the technology improves and costs plummet over the next decade, we expect low carbon heating systems will become the obvious, affordable choice for consumers.”

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