Air Source Heat Pump vs Ground Source Heat Pump

Air source heat pump vs ground source heat pump comes down to where the heat comes from. An air source unit takes it from the outside air, and a ground source unit takes it from the ground through buried pipework. Both then use it to heat your home and hot water. For most UK homes, especially in London, an air source heat pump is the practical choice. It costs less, goes in quickly and needs only a spot for an outdoor unit. A ground source system is usually more efficient, but it needs a lot of land, extensive groundwork and a higher budget. In England and Wales, the Boiler Upgrade Scheme gives £7,500 towards either type.

How Do Air Source and Ground Source Heat Pumps Work?

Both types move heat rather than create it. A refrigerant circuit collects low-grade heat from outside, a compressor lifts it to a useful temperature, and the heat goes into your radiators, underfloor heating and hot water cylinder. Because a unit moves more heat than the electricity it uses, it can deliver several units of heat for each unit of electricity.

The difference is the heat source. Air temperature swings with the season and between day and night, while the ground stays steadier through the year. That is the main reason ground source systems tend to be more efficient.

What Is an Air Source Heat Pump?

An air source heat pump has an outdoor unit with a fan that draws air across a coil. Most homes use an air-to-water system, which heats your wet central heating and hot water. There are two layouts. A monoblock keeps everything in the outdoor unit and connects to the house with water pipes. A split system has the outdoor unit plus an indoor unit that holds the refrigerant components.

Advantages

• Lower installed cost than ground source
• No digging, so installation is quicker and tidier
• Suits smaller plots, since it needs only an outdoor wall or patch of ground
• Qualifies for the same £7,500 grant in England and Wales

Drawbacks

• Efficiency falls as the air gets colder, just when you need the most heat
• The outdoor unit makes noise and needs the right siting
• Planning rules can apply, especially in conservation areas and for flats

What Is a Ground Source Heat Pump?

A ground source heat pump circulates fluid through pipes buried in the ground, collects the stored heat and brings it to an indoor unit. The pipework, called a ground loop, comes in two forms. A horizontal loop is laid in trenches across a large garden. A vertical loop uses one or more boreholes drilled deep into the ground, which needs less surface area but heavy drilling equipment and access.

Advantages

• Usually higher efficiency, particularly in the coldest weather
• No outdoor unit, so nothing to hear or see once the groundwork is finished
• The ground loop itself lasts a long time

Drawbacks

• Higher installed cost, mainly because of the trenches or boreholes
• Needs a lot of land or room for drilling, which most London properties don’t have
• Installation is slower and more disruptive, and may need surveys and permissions

Cost: Installation and the Boiler Upgrade Scheme

For air source, the median installed price in England and Wales in spring 2026 was a little under £13,000 before the grant. The £7,500 Boiler Upgrade Scheme brings that to roughly £5,400. Energy Saving Trust puts a typical ground source installation at around £15,000 with trenches, and borehole drilling can push it a good deal higher, though the exact figure depends on the plot and the ground conditions. Get at least three quotes either way. Homes that need new radiators, a bigger cylinder or an electrical upgrade pay more.

Homes in England and Wales that heat with oil or LPG can qualify for a higher £9,000 grant until 31 March 2027, so ask your installer which level applies to you. Qualifying heat pump installations are also currently zero-rated for VAT until the same date. The grant comes off your bill upfront and applies when you replace a gas, oil, LPG or direct electric heating system. Your installer applies on your behalf and must be MCS certified, so check their certification before accepting a quote. Grant levels and eligibility change, so confirm the current terms on GOV.UK.

Efficiency and Running Costs

Efficiency is shown as a seasonal coefficient of performance, or SCOP: the heat produced per unit of electricity over a year. A typical UK air source heat pump sits around 3. Ground source systems usually do better because the ground temperature doesn’t fall as far in winter, though the exact figure depends on the installation.

A high SCOP doesn’t automatically mean cheap bills. At the standard price-capped rate, a unit of electricity costs several times more than a unit of gas, so running costs depend heavily on your tariff and on how well the system is designed. A heat pump tariff with cheaper off-peak rates can make a real difference. Oversized flow temperatures and undersized radiators both push the efficiency down, so a proper heat loss calculation matters more than the type of heat pump.

How Do They Cope With a UK Winter?

Both types work through British winters, including below freezing. An air source unit loses some efficiency on the coldest days and periodically runs a short defrost cycle to clear ice from the outdoor coil. A ground source system pulls from soil that stays much closer to a constant temperature, so its output changes far less from season to season. Manufacturers also publish lower output ratings at very low outdoor temperatures, so a unit sized for the coldest day should be checked against those figures, not the headline rating. In practice, how a system performs in January depends more on the insulation, the radiator sizes and the flow temperature it was designed around than on which type you pick.

Radiators and underfloor heating can both work with either type. Underfloor heating suits low flow temperatures well, while older radiators often need to be swapped for larger ones. Hot water comes from a cylinder, which usually has to be larger than a gas boiler setup needs.

Space, Planning and Noise

An air source outdoor unit needs a clear, ventilated spot, and its noise is regulated. In England it can generally be installed without planning permission if it meets the permitted development conditions, including the MCS 020(a) noise assessment. That assessment limits the calculated sound to 37 dB(A) at the nearest habitable room window of a neighbouring property. Listed buildings always need permission, and in a conservation area the unit can’t sit on a wall or roof facing the road. Check with your local council first, because local conditions can remove these rights.

Ground source avoids the outdoor unit, so noise is rarely an issue, but the groundwork takes space most London homes can’t offer. As a rough guide, a horizontal ground loop often needs an area around twice the floor area of the house, while a borehole needs room for a drilling rig and access for it. Either way, the garden is the main test. A flat or terrace with a small yard is usually a poor candidate.

Space inside the house matters too. Both types usually need a larger hot water cylinder, and many installs add a buffer tank, so you may need a cupboard or utility room with more floor space than your current boiler takes up.

Maintenance and Lifespan

Both types need an annual check to keep performance and any manufacturer warranty in place. For air source, that includes keeping the outdoor unit clear of leaves and debris. Manufacturers quote different lifespans, generally somewhere between 15 and 25 years for the heat pump unit, with the buried ground loop lasting considerably longer. Sellers’ figures depend on the product and on servicing, so treat them as estimates.

Which Heat Pump Suits Your Home?

Check the Home Before the Heat Pump

A heat pump works best at lower flow temperatures, so the house needs enough insulation and radiators big enough to heat the rooms at those temperatures. Ask any installer for a room-by-room heat loss calculation and an explanation of which radiators would change. Our guide to air source heat pump radiator sizing explains how radiator output is worked out at lower flow temperatures. Without one, you risk cold rooms or a system that works harder than it should.

If a Heat Pump Isn’t the Right Fit

A heat pump isn’t suitable for every home or budget, and a modern efficient boiler remains a sensible choice for many. If you are weighing that route, it helps to know how to calculate boiler size so you don’t buy more boiler than the house needs. If you only want to heat or cool individual rooms without wet radiators, an air to air heat pump installation is a separate option. BeFix provides boiler installation London and boiler repair in London through Gas Safe registered engineers. We offer same-day repair appointments, subject to availability, with engineers typically arriving within 1 to 3 hours, and repairs carry a 12-month workmanship warranty.

You can book a boiler repair online, call 020 8058 4241 or email info@befix.co.uk. We’re open Monday to Friday 7AM to 10PM and Saturday and Sunday 9AM to 8PM at 227B Nether Street, London N3 1NT.

FAQs

What is the main difference between air source and ground source heat pumps?

The heat source. Air source pumps take heat from outside air, and ground source pumps take it from the ground through buried pipes. Everything else follows from that: cost, space, efficiency and disruption.

Is a ground source heat pump more efficient than an air source one?

Usually, yes, because the ground stays at a steadier temperature than the air, particularly in winter. How much better depends on the design and installation, so ask for the predicted SCOP in your quote.

Which is cheaper to install?

Air source. It needs no groundwork. The median installed cost in spring 2026 was a little under £13,000 before the £7,500 grant. Ground source costs more because of the trenches or boreholes.

Do both qualify for the Boiler Upgrade Scheme?

Yes. In England and Wales, the grant is £7,500 for either type, taken off your bill by an MCS-certified installer. Check GOV.UK for current terms before you commit.

Do I need planning permission for an air source heat pump?

Often not in England, if the unit meets the permitted development conditions, including the MCS 020(a) noise assessment, which sets a limit of 37 dB(A) at a neighbour’s habitable room window. Listed buildings always need permission, and conservation areas have extra siting limits, so check with your council.

Can I fit a ground source heat pump in a London home?

Only if you have enough land for trenches or room for a drilling rig, which most London properties lack. For many homes, air source is the realistic option.

Are heat pumps cheaper to run than gas boilers?

Not automatically. Electricity costs more per unit than gas, so savings depend on your tariff, how efficient the system is and how well the home is insulated. A heat pump tariff can help considerably.

How long do heat pumps last?

Manufacturers quote roughly 15 to 25 years for the unit, and a buried ground loop should last longer. Annual servicing helps protect both the lifespan and your warranty.

Does my home need changes before a heat pump?

Often yes: better insulation, larger radiators or a new hot water cylinder. A proper room-by-room heat loss calculation will tell you what’s needed.