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How a heat pump could work for your home

If you're looking to ditch the gas or oil-guzzling boiler and free yourself from spiralling energy costs, heat pumps are an increasingly popular heating option for homeowners across the UK.

As well as being emission-free, air source heat pumps are one of the most efficient ways to heat your home. With traditional boilers running at around 90% efficiency rates, you're losing 10% of the heat generated by burning fossil fuels. Heat pumps have an efficiency rating of around 350%, meaning that the energy used to create the heat for your home is more than tripled as an output.

Around 80% of homes in the UK are currently heated by gas, creating nearly 1/5 of our national greenhouse gas emissions. As part of our journey to net zero, the government has pledged to phase out the installation of new gas boilers by 2035.

Heat pumps are already a popular heating option across Europe, and work in temperatues as low as -20°C.

There are two main types of heat pump; air source and ground source. We look into the main differences to find out which type of homes they work best for, how they heat your home, and whether one could work for you.

How do air source heat pumps work?

Air source heat pumps work in a similar way to a fridge, but in reverse - instead of burning fuel to create heat, they absorb heat from the air outside, and use this to heat your home.

By compressing a refridgerant, air source heat pumps generate heat which can be circulated to your heating system.

There are two main types of air source heat pumps; air-to-water and air-to-air. The difference lies in what form the heat takes when passed to your home.

Air-to-water heat pumps warm your wet central heating system. They need a larger surface area to release heat into your home (like a big radiator or underfloor heating), and the hot water can also be stored in a cylinder for hot showers, baths and taps. Air-to-water heat pumps are more straightforward to integrate into your existing central heating system, and are the most common type of heat pump in the UK.

Air-to-air heat pumps use fans to circulate warm air around your home, instead of radiators. In summer, you can run an air-to-air heat pump to cool your home, too! However, air-to-air systems cannot product hot water, so you'll need a second immersion heater or similar water heating system as well.

Air source heat pumps use electricity to run, but since this is less electrical energy than the heat that it produces, they are an energy-efficient way to heat your home.

Visually, an air source heat pump looks similar to an air conditioning unit, and are installed on an outside wall of your property. You'll also have a hot water cylinder inside your home.

Which houses are suitable for air source heat pumps?

It's important to note that, while air source heat pumps can work really well for some homes, they're not suitable for all types of property.

Firstly, you'll want to make sure that your home is insulated as well as possible, so that it can retain the heat. Homes with drafts, poorly insulated walls or single-glazed windows, such as older properties, are less likely to feel the benefits of a heat pump, so it's wise to address your home insulation and air-tightness first.

Homes built with solid brick walls, insufficient insulation, or restricted space (like flats, mid-terrace buildings and high rises) are less likely to be a good fit for air source heating.

If you're opting for an air-to-water heat pump, you may need to upgrade your radiators to a larger size to get the most out of your system.

You'll also need space for the outside unit, with room around it for airflow, and space inside for the control unit and hot water storage tank (similar to the space needed for a boiler and water cylinder).

You won't normally need planning permission for an air source heat pump, but if you live in a listed building or conservation area, then you may need consent from your local authority.

How much do air source heat pumps cost?

According to Energy Saving Trust, a new air source heat pump can cost between £7,000 - £13,000, depending on the size of your home and type of pump needed.

The government's Boiler Upgrade Scheme means that you could save up to £7,500 of the cost and installation of an air source heat pump - making the cost more comparable to installing a new gas boiler. As heat pumps rise in popularity, we can expect prices to fall further.

The average home can expect to save up to £910 on heating bills compared to an old gas boiler, £1900 when compared to electric storage heaters, £2200 compared to an oil boiler, and £3400 compared to an LPG boiler.

How do ground source heat pumps work?

A ground source heat pump system harnesses natural heat from deep underground. It works by pumping water through pipes buried under the earth, absorbing heat into the water, which is then compressed and passed through a heat exchanger to extract the heat. The heat is then transferred to your home heating and hot water system.

Like air source heat pumps, ground source heat pumps need electricity to run, but the idea is that they use less electrical energy than the equivalent in heat energy that they produce.

Ground source heat pumps work all year round, and can provide both heating and hot water for your home, through radiators.

Which houses are suitable for ground source heat pumps?

To fit a new ground source heat pump, you'll need plenty of space, and a garden with enough access for specialist digging equipment.

The size of the pipe system depends on how big your home is, and how much heat you'll need from your system. Systems can be laid horizontally (for example, two 30m trenches for an average home) or vertically if space is limited, via a borehole 75-200m deep.

You'll also need space inside your home for the indoor heat pump unit, which is roughly the size of a large fridge freezer.

Ground source heat pumps tend to be better suited to new build homes, or homes undergoing significant renovation work, as the installation process can be planned as part of the wider construction work.

As with an air source heat pump, you'll get the most benefit from the system by maximising your home's energy efficiency through loft and cavity wall insulation.

How much do ground source heat pumps cost?

According to Energy Saving Trust, the typical cost of a ground source heat pump is around £24,000 for a horizontal trench installation, and £49,000 for a vertical system. Which? also offer a more detailed breakdown of costs and savings.

With the government's Boiler Upgrade Scheme, you could get up to £7,500 towards the cost of a ground-source heat pump.

The average home could save up to £1000 per year on fuel bills with a ground source heat pump compared to a gas boiler, £2000 a year compared to electric storage heaters, £24000 compared to oil, and £3600 compated to LPG.

How to get started

Whether you make the switch now or further down the line, we'll all need to embrace carbon neutral energy by 2035. The sooner we can lower our emissions, the sooner we can tackle the climate crisis together - and with the current government incentive set to run until 2025, there's never been a better time to install a new heat pump.

We'd always recommend getting at least three quotes from reputable local suppliers, to give you an idea of the market costs for a new heat pump for your home. Your installer will also be able to recommend any efficient-boosting measured you can take to make your home more suitable for a heat pump.

Octopus Energy are helping the UK to switch to heat pumps by offering surveys, quotes and installation of heat pumps, as well as a home heating app and dedicated aftercare. Octopus Energy have invested £10 million in the Uk's first heat pump research and development centre to train up new heat pump installers, with the aim of training 1,000 engineers a year here.

Kensa are the UK's leading ground source heat pump specialists, offering solutions for homeowners and developers, as well as answering frequently asked questions in more detail.

CLPM break down the benefits of ground source vs air source heat pumps below...