Air Source Heat Pump vs Ground Source Heat Pump
Air Source vs Ground Source Heat Pump: Which Should You Get?
If you're trying to choose between an air source heat pump (ASHP) and a ground source heat pump (GSHP), here's the honest answer for most people: get the air source. It costs half the price, it's far easier to install, and it doesn't require digging up your garden. Ground source is genuinely impressive technology — but the extra cost rarely makes sense for a typical UK home.
Let me break down exactly why.
The Numbers Side by Side
| Feature | Air Source Heat Pump | Ground Source Heat Pump |
|---|---|---|
| Installation cost | £8,000–£14,000 | £15,000–£35,000 |
| After £7,500 BUS grant | £500–£6,500 | £7,500–£27,500 |
| Efficiency (COP) | 3.0–4.0 | 3.5–5.0 |
| Space needed | Small outdoor unit (wall or ground) | Large garden for trenches, or borehole drilling |
| Noise | Some (similar to a fridge) | Near-silent |
| Maintenance | Low — annual service | Very low — ground loop rarely needs attention |
| Lifespan | ~20 years | 25–30 years |
| BUS grant available | £7,500 | £7,500 |
Why Air Source Wins for Most People
Nine out of ten heat pump installations in the UK are air source. That's not a coincidence.
The biggest factor is cost. Even after the £7,500 Boiler Upgrade Scheme grant, a ground source system can cost you £10,000–£20,000 more than an air source equivalent. That's a lot of money to recover through slightly better efficiency. In most cases, you'd be waiting 30+ years to break even on the difference — if ever.
Then there's the installation. An air source heat pump goes in within a day or two. A small unit sits outside your house, connected to your heating system. That's it. Ground source is a much bigger project. You either need extensive trenches dug across your garden (you'll need at least 600–800m² of land) or a borehole drilled 100m+ into the ground. Both options are disruptive and add significantly to the cost.
Yes, ground source is more efficient — a COP of up to 5.0 versus up to 4.0 for air source. That means lower running costs. But the gap isn't large enough to justify the price difference for most homes.
When Ground Source Actually Makes Sense
There are genuine cases where ground source is the right call. You should consider it if:
- You have a large plot of land — at least half an acre — and you're not fussed about trenches
- You're building a new property and can factor the extra cost into the build
- You're installing in a very rural area where noise from an air source unit would be unwanted
- You want the absolute lowest possible running costs and you're in it for the long term
- You have an exceptionally large or heat-hungry property where the efficiency gap really adds up
If you have a reasonably sized garden and money isn't a constraint, ground source is a genuinely excellent system. It's quieter, marginally more efficient, and it lasts longer. The ground temperature stays consistent year-round, which means it doesn't struggle in cold snaps the way air source can.
The Cold Weather Question
One common concern about air source pumps is performance in cold weather. Modern ASHPs handle this much better than older models — most continue working down to -15°C or -20°C. Yes, efficiency drops a little in a cold snap. But unless you're in the Scottish Highlands and routinely see temperatures below -10°C, this shouldn't be a deciding factor.
Ground source doesn't have this problem — the ground sits at a stable 10–12°C year-round. But again, for most UK homes, this advantage isn't worth the price premium.
What About Noise?
Air source units do make some noise. Not a lot — similar to a quiet air conditioning unit or a fridge. But if your neighbour's bedroom window is directly next to where the unit would go, it's worth thinking about placement. Ground source systems are essentially silent once installed.
That said, planning rules in England, Wales, and Scotland have specific requirements about siting heat pump units away from windows and boundaries, so a good installer will help you find a sensible position.
The Bottom Line
For most UK homeowners — especially those in towns, suburbs, or homes with normal-sized gardens — air source is the clear winner. It's cheaper upfront, simpler to install, and the efficiency difference doesn't justify paying an extra £10,000–£20,000.
Get ground source if you have the land, the budget, and you want to squeeze every last bit of efficiency from your heating system. It's genuinely great technology. But don't let anyone tell you it's necessary for a comfortable, efficient home. Air source does the job brilliantly for the vast majority of people. For help choosing a specific model, see our best heat pumps UK guide and our heat pump costs guide.