Air source vs ground source heat pumps

Choosing between an air source and a ground source heat pump is a significant decision for homeowners looking to invest in their home's heating. This guide offers a clear, data-backed comparison to help you understand the differences, benefits, and considerations for each system, empowering you to make an informed choice for a future with more control over your energy use.

Understanding heat pumps: the basics

How heat pumps work

Heat pumps do not generate heat; instead, they transfer it, making them highly efficient for heating and, in some cases, cooling your home. They extract low-grade heat from an external source - either the air or the ground - and then upgrade it to a higher temperature for use in your central heating system and hot water. This process uses electricity to move heat, rather than create it, allowing them to deliver more energy than they consume.

Why consider a heat pump for your home?

Heat pumps offer a pathway to long-term energy savings and resilience against fluctuating energy prices, alongside reducing carbon emissions compared to traditional fossil fuel boilers. They are a long-term investment towards reducing your carbon footprint and achieving greater energy independence. Optimal performance and running costs are heavily influenced by your home's insulation levels and smart energy management.

Air source heat pumps explained

How they work

Air source heat pumps (ASHPs) absorb heat from the outside air, even at low temperatures, and use it to warm your home and hot water. They function much like a refrigerator in reverse, using a compressor and refrigerant to transfer heat from the air outside into your property's heating system. There are two main types: air-to-water, which provides hot water and central heating, and air-to-air, which provides warm air through fans for space heating only.

Pros and cons

• Lower installation cost: Generally cheaper to install than ground source heat pumps.

• Easier installation: Installation is typically less disruptive and quicker, usually taking 3-5 days.

• Versatility: Can provide both heating and cooling.

• Reduced emissions: Significantly lower carbon emissions compared to fossil fuel boilers.

• Government grants: Eligible for the Boiler Upgrade Scheme.

• Outdoor unit: Requires an external unit, which can be visually noticeable and produces a low hum.

• Efficiency in extreme cold: While modern units can operate in very low temperatures, their efficiency can dip in sustained extreme cold.

• Hot water cylinder: Often requires space for a hot water cylinder if your home currently uses a combi boiler.

• Insulation dependent: Work most efficiently in well-insulated homes; insulation upgrades may be necessary.

Typical installation considerations

An air source heat pump unit needs an outdoor space of about 2m x 1m, with at least 30cm clear space around the back and sides, and 1.5m in front for adequate airflow. It should be located where its operational hum will not cause disturbance. If your home lacks a hot water storage tank, one will need to be installed.

Ground source heat pumps explained

How they work

Ground source heat pumps (GSHPs) extract heat from the ground via buried pipework, which contains a mixture of water and antifreeze. The ground's temperature remains relatively stable throughout the year, allowing GSHPs to deliver consistent and efficient heating and cooling performance regardless of external weather conditions. The absorbed heat is then transferred to a refrigerant, compressed, and used to heat your home and hot water.

Pros and cons

• High efficiency: Generally more energy-efficient than air source heat pumps due to the stable ground temperature.

• Long lifespan: The underground pipework can last up to 100 years, with the indoor unit typically lasting 25 years.

• Quiet operation: Very quiet, as the main components are indoors and underground.

• Consistent performance: Less affected by extreme outdoor air temperatures.

• Government grants: Eligible for the Boiler Upgrade Scheme.

• High installation cost: Significantly more expensive to install due to the extensive groundwork required for burying pipes or drilling boreholes.

• Disruptive installation: The installation process is more complex and disruptive, potentially taking 1-4 weeks.

• Space requirements: Requires substantial outdoor space for horizontal ground loops (2-3 times your home's floor area) or boreholes for vertical installations.

• Suitability: Not suitable for properties with limited outdoor space.

Typical installation considerations

Installing a ground source heat pump involves significant groundwork, either digging trenches for horizontal loops or drilling boreholes for vertical loops. Horizontal loops typically require 2-3 times your home's floor area in garden space. Vertical installations, while taking up less surface area, require specialist drilling equipment. The indoor unit typically resembles a large cabinet.

Direct comparison: air source vs ground source

Installation costs and running costs

Air source heat pumps typically cost between £7,000 and £15,000 to install in the UK, according to Thermal Earth. Ground source heat pumps are more expensive, with installation costs generally ranging from £15,000 to £50,000.

While ground source systems have higher upfront costs, they can offer lower running costs due to their greater efficiency and the stable temperature of the ground. Air source heat pumps, though cheaper to install, might require more electricity during very cold periods.

Efficiency and performance

Heat pumps can achieve efficiencies (Seasonal Coefficient of Performance, or SCOP) of 300% or more, meaning they produce 3 or more units of heat for every unit of electricity consumed. SCOP is a crucial metric that measures a heat pump's average efficiency over an entire heating season, accounting for varying outdoor temperatures. A SCOP of 3.5 or above is considered good, with anything over 4.0 being excellent.

Ground source heat pumps generally perform better over the year than air source units because ground temperature is more stable. This consistent temperature allows GSHPs to maintain a steadier SCOP, whereas ASHP efficiency can dip slightly in colder weather.

Lifespan and maintenance

Both types of heat pumps are built to last. Air source heat pumps typically have a lifespan of 15-20 years, with some lasting longer with proper maintenance. Ground source heat pumps often last longer, with the indoor unit lasting up to 25 years and the underground pipework potentially lasting up to 100 years.

Annual servicing is recommended for both systems to ensure optimal performance and maintain manufacturer warranties.

Space requirements and suitability

Air source heat pumps require a relatively small outdoor space for the unit, typically around 2m x 1m, plus indoor space for a hot water cylinder if needed. They are generally suitable for most homes, including those with smaller gardens or in urban areas.

Ground source heat pumps demand significantly more outdoor space for the ground loops. Horizontal installations need a large area for trenches, while vertical installations require boreholes. This makes them more suitable for properties with ample land.

Government grants and financial support

The Boiler Upgrade Scheme (BUS)

The Boiler Upgrade Scheme (BUS) is a government initiative in England and Wales designed to help homeowners reduce the upfront cost of installing low carbon heating systems. The scheme offers grants of £7,500 towards the cost of installing an air source or ground source heat pump, according to the UK Government.

For homes in England and Wales replacing heating oil or LPG systems, the grant increased to £9,000 from 21 July 2026 until 31 March 2027. To be eligible for the BUS grant, heat pump installations must be carried out by an MCS-certified installer, who will apply for the grant on behalf of the homeowner.

Other potential incentives

While the BUS is the primary grant for heat pump installations, other potential incentives may become available. It is always advisable to check local and regional schemes, as well as any new government announcements, for additional support.

Maximising your heat pump's potential with Fuse Energy

Choosing a heat pump is a power play for your home's future; choosing Fuse Energy is how you win it by optimising running costs and control. Fuse Energy does not install heat pumps, but focuses on optimising the energy supply and management for heat pump owners.

Optimising running costs with smart tariffs

Heat pumps are highly efficient, but their operational costs can be further reduced by aligning their usage with smart energy tariffs. Fuse's smart tariffs can help heat pump owners reduce operational costs by running their systems during periods of cheaper, abundant energy. This approach shifts the focus from 'using less' to 'having more' control over home comfort and energy use.

Empowering control with the Fuse app

The Fuse app provides real-time consumption data, empowering homeowners to monitor and manage their heat pump's energy usage effectively. This capability allows you to see exactly how much energy your heat pump is using and make informed decisions to manage your home's climate more economically.

A future with power to play with

Fuse's vision of abundant energy aligns with heat pump adoption, offering a future where energy is so plentiful it stops being a constant concern. By combining the efficiency of heat pumps with smart energy management through the Fuse app and tariffs, homeowners gain greater independence and control, transforming their energy consumption into a strategic advantage.