If you're considering replacing your boiler with a heat pump, you'll usually come across two main options:

air source heat pumps and ground source heat pumps.

Both use electricity to move naturally occurring heat into your home, but they collect that heat from very different places.

An air source heat pump takes heat from the outside air.

A ground source heat pump takes it from the ground beneath your property.

That one difference affects almost everything else, including installation cost, efficiency, disruption, space requirements and which type actually makes sense for the average UK home.

So, which is better?

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Air source vs ground source heat pumps at a glance

In simple terms, ground source heat pumps usually win on efficiency, while air source heat pumps win on cost and practicality.

For most UK homeowners, that makes air source the more realistic option.

What is an air source heat pump?

An air source heat pump extracts thermal energy from the outside air and uses it to heat your home.

And yes, it can still do this when it's cold outside.

Even at sub-zero temperatures, the air still contains usable heat energy. The heat pump absorbs that energy into a refrigerant before a compressor raises its temperature to a level suitable for heating your home.

Most domestic installations in the UK use an air-to-water heat pump.

These supply warm water to:

• radiators

• underfloor heating

• a hot water cylinder

Think of it as a refrigerator working backwards.

Except instead of protecting a questionable tub of hummus, it's heating your house.

What is a ground source heat pump?

A ground source heat pump works on the same basic principle, except it takes heat from the ground rather than the air.

A network of pipes is installed underground and filled with a heat-transfer fluid.

As that fluid circulates through the ground, it absorbs naturally occurring heat before returning to the heat pump, where the temperature is raised and transferred into your heating system.

There are generally two ways of installing the ground loop.

Horizontal ground loops

Long lengths of pipe are buried in trenches across your land.

This is usually the cheaper option, but it requires a reasonably large amount of accessible outdoor space.

Vertical boreholes

Where there isn't enough land for horizontal trenches, boreholes can be drilled deep underground instead.

This is one of the main reasons ground source heat pump prices vary so widely.

Which is more efficient?

Generally, ground source heat pumps are slightly more efficient and more consistent throughout the year.

The reason is fairly simple.

Air temperatures in Britain move around quite a lot.

A heat pump operating when it's 12°C outside has an easier job than one operating when it's -3°C.

Ground temperatures, however, remain much more stable.

That means a ground source heat pump is drawing heat from a relatively consistent source even during winter.

The smaller the temperature difference between the heat source and the temperature your heating system needs to produce, the less work the heat pump generally has to do.

So ground source has a technical advantage.

But efficiency isn't the only thing that matters.

Saving a little more electricity every year doesn't automatically justify spending substantially more money installing the system in the first place.

Do air source heat pumps work in winter?

Yes.

Modern air source heat pumps are designed to operate at temperatures well below those normally experienced across most of the UK.

Their efficiency does generally fall as the outside temperature drops, but that isn't the same as the heat pump suddenly failing when there's frost on the car.

The real issue is system design.

A properly specified heat pump needs to be capable of meeting the property's heat demand at its expected winter design temperature.

That means carrying out proper heat-loss calculations rather than simply replacing a 30kW boiler with a 30kW heat pump and hoping nobody notices.

How much does an air source heat pump cost?

There isn't one particularly useful fixed price.

Air source heat pump installations vary according to:

• the size and heat loss of the property

• the heat pump required

• radiator upgrades

• hot water cylinder requirements

• electrical work

• pipework

• installation complexity

Government policy has increasingly focused on reducing this upfront cost through the Boiler Upgrade Scheme rather than prescribing a standard retail price.

For eligible properties in England and Wales, the standard BUS grant is currently £7,500 towards an air-to-water heat pump.

That can remove a very significant chunk of the installation cost.

How much does a ground source heat pump cost?

Ground source systems are generally more expensive to install.

The reason isn't necessarily the heat pump itself.

It's what needs to happen underneath your feet.

You may need:

• substantial trench excavation

• hundreds of metres of buried pipe

• specialist drilling

• boreholes

• additional groundworks

• reinstatement of the land afterwards

The cost therefore varies enormously depending on the property.

A house with a large accessible field where horizontal loops can be installed is a very different project from one requiring deep vertical boreholes.

What can be said with confidence is that ground source installations are usually more expensive upfront than equivalent air source systems, and boreholes can increase that difference considerably.

What heat pump grants are available?

For homes in England and Wales, both air-to-water and ground source heat pumps can currently qualify for the Boiler Upgrade Scheme.

The standard grant values are:

• £7,500 for an air-to-water heat pump

• £7,500 for a ground source heat pump

• £2,500 for an air-to-air heat pump

The scheme is administered by Ofgem on behalf of the Department for Energy Security and Net Zero.

There is also currently an enhanced grant for some off-gas-grid properties.

Until 31 March 2027, eligible homes that have no mains gas connection and are replacing an oil or LPG heating system can receive £9,000 towards an air-to-water or ground source heat pump. Ofgem

The scheme is installer-led.

Your MCS-certified installer submits the application, and the value of the grant is reflected in the price you pay rather than being paid directly into your bank account afterwards. Ofgem

What about VAT?

Qualifying heat pump installations currently benefit from 0% VAT until 31 March 2027.

That applies to energy-saving materials including heat pumps and can reduce the upfront cost further. Ofgem

Does the grant make ground source much cheaper?

It helps.

But it doesn't remove the fundamental cost difference.

Both air-to-water and ground source heat pumps receive the same standard £7,500 grant.

If an air source system requires relatively straightforward installation work, that grant can represent a substantial proportion of the total cost.

A ground source system may still require significant expenditure on trenches, drilling or boreholes.

So although the government support is equal, the amount you need to fund yourself may not be.

What space does an air source heat pump need?

Not a huge amount.

You'll need an appropriate outdoor location for the heat pump unit with sufficient airflow around it.

Inside the property, you may also need room for:

• a hot water cylinder

• controls

• pipework

• potentially a buffer vessel or volumiser

The outdoor unit needs to be positioned sensibly.

That means considering airflow, access, noise and the distance between the unit and the rest of the heating system.

What space does a ground source heat pump need?

Potentially quite a lot.

Horizontal ground loops require enough land for trenches to be excavated and the pipework installed.

How much land you need depends on things including:

• property heat demand

• ground conditions

• loop design

• available excavation area

The site also needs to be accessible to the equipment carrying out the work.

If you don't have enough land, vertical boreholes may be possible instead.

These take up considerably less surface space but require specialist drilling, which pushes costs higher.

Once horizontal loops have been installed, the trenches are filled back in and the land above can generally be used again.

So you're not permanently sacrificing the garden.

You just have to temporarily accept that it may look like somebody has started looking for Roman pottery.

Do both types need new radiators?

Possibly.

This isn't really an air source versus ground source issue.

Both heat pumps usually operate most efficiently at lower flow temperatures than a traditional gas boiler.

That means the heating system needs enough surface area to deliver sufficient heat into each room.

Depending on your heat-loss assessment, you may need to:

• keep existing radiators

• increase the size of some radiators

• install higher-output radiators

• use underfloor heating

Some homes will require very few changes.

Others will require more.

The key point is that the system should be designed around the heat requirements of the property.

Air source heat pump pros and cons

Advantages of air source heat pumps

Lower installation cost

They normally require much less groundwork than ground source systems.

Easier installation

There are no underground loops or deep boreholes to install.

Suitable for far more UK homes

You don't need a huge garden.

Generous government support

Air-to-water systems qualify for the same standard £7,500 Boiler Upgrade Scheme grant as ground source systems.

Wide range of systems

Manufacturers including Vaillant, Daikin, Viessmann and others now offer heat pumps designed specifically for European climates.

Disadvantages of air source heat pumps

Efficiency varies with outside temperature

They generally have to work harder when outdoor temperatures fall.

Visible outdoor unit

Some homeowners simply don't like how they look.

Some operational noise

Modern premium units can be extremely quiet, but they still use a fan and compressor.

Slightly lower seasonal efficiency

All else being equal, ground source usually has the edge.

Ground source heat pump pros and cons

Advantages of ground source heat pumps

Higher and more stable efficiency

The ground offers a relatively consistent heat source throughout the year.

Strong winter performance

Cold air temperatures have much less effect on the temperature underground.

No conventional outdoor fan unit

Most of the collection system is hidden below ground.

Long-lasting ground infrastructure

The underground pipework can potentially remain in service for a very long time, even if the heat pump itself is eventually replaced.

Excellent option for the right rural property

If you've got plenty of land, one of ground source's biggest drawbacks becomes considerably less important.

Disadvantages of ground source heat pumps

Higher upfront cost

The groundworks can make installations much more expensive.

Far more disruptive installation

Horizontal systems involve trenching, while vertical systems require specialist drilling.

Space requirements

Many UK homes simply don't have enough suitable land.

Same standard BUS grant

The £7,500 grant is valuable, but the starting installation cost can still be considerably higher.

Which is quieter?

Ground source wins outside the property.

There is no conventional outdoor fan unit moving large volumes of air.

Air source heat pumps do produce some sound from the fan and compressor.

That said, modern units can be impressively quiet.

Good positioning and correct installation also matter enormously.

A well-sited premium air source heat pump can be far less noticeable than many homeowners expect.

Which lasts longer?

Both systems should provide many years of service when properly installed and maintained.

Ground source does have one interesting long-term advantage.

The underground ground loop can have a very long working life.

So when the heat pump itself eventually needs replacing, some of the expensive underground infrastructure may still be reusable.

Air source systems don't have that same buried infrastructure.

But they are cheaper and simpler to install in the first place.

It's another example of the same trade-off running through this entire comparison:

ground source often wins technically, while air source often wins practically.

Which is better for the average UK home?

For most properties, air source.

Not because it beats ground source in every technical category.

It doesn't.

Ground source offers:

• more stable source temperatures

• potentially higher seasonal efficiency

• no outdoor fan unit

• excellent cold-weather consistency

But most UK homeowners aren't choosing a heating system in an engineering laboratory with an unlimited budget and several spare acres behind the conservatory.

Air source heat pumps are:

• cheaper to install

• easier to fit

• suitable for more properties

• less disruptive

• eligible for the same standard £7,500 BUS grant

For the majority of homeowners, that makes them the more sensible option.

When does ground source make more sense?

Ground source becomes much more attractive if you:

• have a large property

• have plenty of accessible land

• are building a new home

• are carrying out a major renovation

• have high heating demand

• intend to stay in the property for a long time

• prioritise maximum long-term efficiency over upfront cost

It can make particularly good sense for larger rural properties where there is already sufficient land for horizontal ground loops.

In those circumstances, the additional complexity becomes much easier to justify.

Air source vs ground source: our verdict

If we're judging purely on engineering elegance, ground source makes a very strong case.

The heat source is stable.

Seasonal efficiency can be excellent.

There's no big fan unit outside.

And the buried infrastructure can last an extremely long time.

But homes aren't spreadsheets.

Cost, disruption and practicality matter.

For the vast majority of UK households, an air source heat pump provides the better overall balance.

You get:

• excellent efficiency

• reliable winter heating

• relatively straightforward installation

• significantly lower upfront costs

• strong government support

Ground source remains a fantastic option where the property and budget justify it.

Air source is simply the option that makes sense for far more people.

And, importantly, choosing air source isn't settling for the budget version of heat pump technology.

A properly designed modern air source system can provide extremely efficient heating throughout the British winter without requiring your back garden to become a civil engineering project.

Thinking about an air source heat pump?

Heatable installs high-efficiency air source heat pumps from leading manufacturers including Vaillant, with every system designed around the individual heat requirements of your home.

You can get an online heat pump quote and see what your installation could cost after any available Boiler Upgrade Scheme support.

Next Steps For Your Heat Pump Journey:

When planning to install a heat pump for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:

• What is the Boiler Upgrade Scheme?

• Is my home suitable for a heat pump?

• How much do heat pumps cost?

• Best heat pump brands.

• What size heat pump do you need?

• Air conditioners pros and cons

• Air conditioning servicing UK

• Aira heat pump review.

• Best heat pump installers

• How efficient are heat pumps?

• Octopus cosy heat pump review

To dive deeper into these topics, head over to our advice section or check out our YouTube channel to learn more.

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