Air Source vs. Ground Source Heat Pumps
Both air source and ground source heat pumps are efficient, low-carbon alternatives to traditional heating systems. The difference lies in where they collect heat: air source heat pumps use the outside air, while ground source heat pumps draw energy from the ground. Because ground temperatures remain consistent throughout the year, ground source heat pumps deliver higher efficiencies, lower running costs and more reliable performance, particularly during colder weather when heating demand is highest. With no outdoor unit, minimal maintenance and a lifespan of around 25 years, they are often the preferred choice where long-term value, reliability and performance are priorities.
Ground source heat pumps are a better long-term choice than air source heat pumps. They combine lower lifetime costs with a seamless “fit and forget” experience that doesn’t compromise how a home looks, sounds or feels.
What’s the difference between a ground source and an air source heat pump?
Ground source heat pumps draw stable heat from the ground, making them consistently more efficient, reliable and lower cost to run than air source heat pumps. They sit inside the home, taking up no more space than a traditional boiler. That means they are discreet as well as durable, since they are protected from the elements. They bring lower energy bills and carbon emissions than air source heat pumps, and can produce – in ideal conditions – up to six times the amount of energy they need to run. With little maintenance required, Kensa models last for up to 25 years. Because the ground temperature is stable all year round – between about 8℃ and 12℃ – you get high efficiencies during the coldest spells.
Air source heat pumps rely on the fluctuating temperature of the air, meaning the colder the temperature outside, the harder the heat pump has to work, and the more expensive the running costs. Efficiencies vary heavily depending on installation and design quality, but air source heat pumps require up to 40% more energy during peak heating periods. Air source heat pumps can be very large: because they sit outside the home and affect the aesthetic look of a home in a residential area, they can require planning permission. Since they are exposed to the elements, and require cycles to defrost, they typically have a much shorter life span (10-15 years) than ground source heat pumps. They also need regular maintenance.
Are ground source heat pumps or air source heat pumps cheaper?
The upfront costs of ground source heat pumps depend on their application, but they tend to be higher than those for air source heat pumps. Over their lifetime it is a completely different story: ground source heat pumps will save a homeowner, resident or multi-asset owner thousands of pounds compared to air source heat pumps. That is because they are much more efficient than air source heat pumps, last much longer, and have fewer maintenance requirements.
SCOP is an industry standard measurement of efficiency across all seasons. Ground source heat pumps achieve SCOPs of between 3.5 and 6. Air source heat pumps typically manage between 2.5 and 3.5 in UK conditions, with their performance dropping most in winter. This means running costs are lower for ground source heat pumps. Coupled with lower maintenance costs, the durability of ground source heat pumps compared to air source heat pumps means lifetime ownership costs are very different. Over 30 years this could mean having enough spare change for a full kitchen replacement – not to be sniffed at!
Which is easier to install?
Ground source heat pumps can be installed by any qualified heating engineer. The ground array can be installed horizontally with slinkies or straight pipes, or vertically, via boreholes. Arrays generally do not require planning permission, since they are considered permitted development. Once they are in place, they are invisible and can be left for 100 years or more, an asset to a home that gives you ultimate peace of mind. The ground source heat pump unit can be fitted into an airing cupboard, utility room, garage or purpose built outdoor enclosure and connects to standard distribution systems in homes (pipework, radiators, underfloor heating).
Air source heat pumps do not require digging but are large outdoor units, similar in appearance to an air conditioning unit you might see on the side of a building, but larger. Since there is a risk of noise pollution, and units change the appearance of a home, they can require planning permission, depending on local authority rules and the character of the area.
Why ground source heat pumps are the smart choice
Ground source heat pumps work in most housing settings:
New build developments
By choosing them for new builds, housebuilders can make the most of the efficiencies of large build programmes to give homebuyers the most desired heating solution, which is compact, discreet and durable. In this context, ground source heat pumps come with the same or lower upfront costs than air source heat pumps and can be fitted without delays as part of a multi-utility package. They enable housebuilders to unlock grid-constrained sites, and save homebuyers almost a fifth in running costs compared to air source heat pumps, while offering on-call maintenance and servicing.
Social housing
In social housing, ground source heat pumps alleviate fuel poverty and bring down asset management costs, with fewer regulatory hurdles than central plant air source heat pumps. They require no central plant rooms or metering and billing and provide a way of bringing down carbon emissions without covering residential buildings with cumbersome outdoor units. Energy bills for homes with ground source heat pumps can be 75% lower if they are replacing direct electric heating, and they allow residents to choose their energy provider and tariff, so that they can shop around for the best deals. Lasting up to 25 years, ground source heat pumps are the most durable heating system, with significantly lower maintenance costs than central plant air source heat pumps (more likely to breakdown and need servicing). While both technologies are delivered as a heat network, networked ground source heat pumps carry a lower regulatory burden and costs.
Individual homes
For individual homes, ground source heat pumps are the least intrusive, most efficient and longest lasting heating option. With no unsightly outdoor unit, no noise complaints and no planning permission required – just an indoor unit that fits in an airing cupboard – they enable homeowners to keep enjoying their home as they fell in love with it. They score highest in efficiency metrics, saving owners up to £1,000 per year compared to air source heat pumps, and leaving them emitting less carbon than their neighbours.