Air source heat pumps: how the costs and savings stack up

Air source heat pumps: how the costs and savings stack up

Households are encouraged to move away from their old gas and oil-fired boilers and replace them with new, clean and environmentally friendly heat pumps.

As the Cop26 climate summit approaches, the UK government plans to offer grants to help households install air source heat pumps and other low-carbon heating systems over the next three years. .

Central heating and hot water account for around 20% of UK carbon emissions. An air source heat pump running on renewable electricity will heat a home much more sustainably, which is why ministers are urging consumers to make the switch.

Questions and answers

What are heat pumps and why is the UK government pushing them?


Simply put, an electric heat pump works like an inverted refrigerator, extracting heat from outside air, soil, or a nearby water source before concentrating the heat and transferring it indoors. They can usually be found on the exterior of a house and look like a standard air conditioning unit.
Around 85% of UK homes use gas boilers for heating, making it one of the most polluting sectors of the economy. The fossil fuels used in our homes for heating, hot water and cooking account for over a fifth of the UK’s carbon emissions, which means low-carbon alternatives are essential if the UK government hopes to meet its climate goals.

Jillian Ambroise

Photograph: KBImages / https: //
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What are they and how do they work?

Simply put, an air source heat pump works like an inverted refrigerator, extracting heat from the outside air before concentrating it and transferring it inside to provide central heating and hot water. The pumps look like a standard air conditioning unit and should be located outside the house. They will operate in temperatures of minus 15 ° C and below, although the colder the outside temperature, the more electricity they must use to heat your home. Geothermal heat pumps work the same way but recover heat from underground pipes. These are more efficient but are more difficult to renovate in existing homes unless you are ready to dig your garden.

An air source heat pump extracts heat from the outside air before concentrating it and transferring it inside to provide hot water and central heating. Photography: Jenny Dettrick/Getty Images

How much does it cost to install one?

Don’t believe some of the quoted prices that have popped up in recent days, someone with a family home with three or more beds can expect to pay £ 8,000-15,000 in total to install a complete air source system , while fitting out a larger house will cost more. In addition to the pump, this price will include a new hot water tank and labor. The final bill will depend on whether your existing radiators are large enough or need to be replaced. It is also advisable to improve your home’s insulation at the same time, which could dramatically increase the final bill, depending on your home’s construction. It will cost much more to install a ground source heat pump, typically over £ 15,000.

What financial assistance is there?

This week the government announced it would provide households with grants of £ 5,000 to help them set up ASHPs, with the total money sufficient to cover 90,000 households. Grants of up to £ 6,000 will be available for ground source heat pumps.

Grants will be available from April 2022, and details on how consumers will apply have yet to be released. The plan will operate for three years. It is highly likely to be oversubscribed, meaning those who meet the criteria fastest will receive the grants.

What has been less publicized is the fact that you can already apply for funding through the Renewable Heat Incentive (RHI). Buyers must pay for the work in advance and then collect RHI payments, which are paid quarterly for the first seven years of ownership. The total amount paid to a household under the RHI depends on the measure installed, the energy performance of the house and the type and age of the boiler to be replaced. Those who replace an old oil-fired boiler receive the most – usually £ 9,000. If you are replacing an old gas boiler in a family home you can expect to receive a total of £ 7,000. There is a calculator on the government website.

To earn RHI money you need to use an MCS accredited installer and there is a somewhat torturous application process. The RHI will close to new requests on March 31, 2022.

what operating cost of air source heat pumps?

People who tear up an old inefficient oil-fired boiler should cut their annual energy bill by switching to an ASHP, but not drastically. Those who buy a gas boiler are very unlikely to save money and may well end up paying more each year. Octopus Energy claims that in a poorly insulated house, it will cost up to 40% more to operate a heat pump rather than a traditional boiler. This is because the cost of electricity includes carbon taxes and subsidies to support low carbon energy projects. Green groups called on the government to shift these levies to gas bills instead of encouraging households to turn their backs on oil and gas.

Do they work as well as a conventional boiler?

A properly installed ASHP system, the right size for the property, should keep the house warm on colder winter days. They typically operate at 55 ° C rather than the 60-80 ° C that gas boilers often operate at, which is why they may require larger radiators. They work particularly well with underfloor heating and are designed to keep indoor spaces a constant temperature with slight additions throughout the day.

What are the disadvantages ?

An aerothermal heat pump
Air-source heat pumps will operate in temperatures of minus 15 ° C and below, although the colder the outside temperature, the more electricity they must use to heat your home. Photograph: KBImages / Alamy

The biggest problem is that a lot of UK homes are not suitable for an ASHP. Apartment owners struggled to get permission, and that assumes the installer has found a way to make a system work in a confined space. Upgrading a system with an existing boiler is not for the faint of heart, as much of the plumbing will need to be replaced. You will also need a place to store a water tank.

There are concerns about the reliability and longevity of some systems. Mitsubishi pumps seem to be well regarded, as do those from Scandinavia and, more recently, the Northern Irish supplier Red. Some settled in coastal towns suffered premature wear due to the high salt content of the air.

Is it worth it?

If you are emptying and restoring a home and installing a brand new heating system with a major insulation upgrade, installing an ASHP – or better yet, a ground source heat pump – with field heating. soil is obvious. Likewise, if you are currently using an old boiler that needs to be replaced anyway.

Whether you want to rip off a modern gas boiler in perfect condition will largely depend on whether you want to switch to zero carbon heating, how well your home is insulated and, if your insulation is poor, whether you are ready to see your elements. bills go up.

Is it worth waiting for an alternative technology to emerge?

May be. Large investments are being made in community geothermal heating systems, where entire roads, properties and towers are hooked up to a central geothermal source that runs under the road. Simon Lomax, who runs Kensa heat pumps in Cornwall, thinks these offer a much better long-term solution as they are more efficient and durable, and don’t have many of the downsides of ASHPs. Hydrogen is the other big hope. Tests and programs test whether the highly flammable element can be used safely.


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