Heat pump types: which one suits your home?

There are five distinct heat pump technologies installed in UK homes. The right choice depends on your property, your garden, your budget, and your time horizon. This page is a side-by-side starting point; each type has a detailed deep-dive linked below.

At-a-glance comparison

SCOP = Seasonal Coefficient of Performance, heat output per unit of electricity, averaged over a year. Higher is better.

Pick a type to read in detail

How to decide between them

For most UK homeowners, the decision tree is:

1. Do you have an outdoor wall and ~1.5 m of clear space in front of it?
   → Yes: ASHP is almost certainly your answer.
2. Do you have substantial grounds (2 – 3× the property footprint) and a higher budget?
   → Worth getting a GSHP quote alongside ASHP for comparison.
3. Is your property next to a river, pond, lake or above a known aquifer?
   → Investigate WSHP, highest efficiency if permits clear.
4. Is it a new-build with MVHR?
   → Ask the architect to model EAHP against full ASHP.
5. Property genuinely can't accept a full retrofit?
   → Look at hybrid, but understand the BUS trade-off.

Why the SCOP numbers differ so much

SCOP (Seasonal Coefficient of Performance) measures how much heat a system delivers per unit of electricity it consumes, averaged across a full year. A SCOP of 4.0 means 1 kWh of electricity in delivers 4 kWh of heat out. The gap between types comes down to one thing: the temperature of the heat source.

Air source pulls heat from outside air, which can be 0°C or below in a UK winter, so the compressor works hard to raise it to a useful temperature, capping real-world SCOP around 2.8 to 4.5. Ground stays at a steady 10 to 12°C even in January, so a GSHP's compressor has less distance to travel, and SCOP climbs to 3.5 to 5.0. Water sources, rivers, lakes and aquifers, rarely drop below 4°C even in a cold snap, which is why WSHPs post the highest SCOPs in the comparison table, 4.0 to 5.5¹. Exhaust air sits in the middle because the extract air it draws on is a stable but limited-volume source at around 20°C, good temperature, small quantity.

In practice, insulation and radiator sizing move SCOP more than the heat pump type does for most homeowners. A poorly insulated home with an undersized radiator system can drag any technology's real-world SCOP down by a full point or more, which is why a proper heat-loss survey matters more than the brand or type you choose. See how to choose an installer for what a competent survey looks like.

Can you combine heat pump types?

Yes, in a handful of legitimate configurations. New-builds sometimes pair a small ASHP for hot water with EAHP for space heating, since EAHPs generally handle hot water less efficiently. Larger rural properties occasionally run a GSHP for the main house and a supplementary ASHP for an extension or outbuilding where trenching to the ground array isn't practical. What doesn't make sense is mixing a full heat pump with a boiler outside the formal hybrid configuration, that just adds cost and complexity without the BUS-excluding trade-off being worth it. If your installer proposes a combination, ask them to justify it against a single well-sized system first.

What to do once you've picked a type

Get three quotes from MCS-certified installers who do that specific technology. Insist on a proper heat-loss survey before any quote. Read our questions to ask guide before you sign anything.

Why air source dominates the UK market

Roughly 90% of heat pumps installed under the Boiler Upgrade Scheme are air source, and that's not an accident of marketing. ASHP is the only technology that works on almost any UK property with an outdoor wall, doesn't need garden space or water access, and has the widest installer base of any type, which keeps quotes competitive. Ground, water and exhaust air all solve a specific problem better than ASHP in the right circumstances, higher efficiency, lower running cost, no outdoor unit, but for most semi-detached and terraced properties without unusual site constraints, the extra cost and complexity of the alternatives isn't justified by the marginal efficiency gain.

Questions to bring to your first installer call

Regardless of which type you're leaning toward, ask every installer the same baseline questions so quotes are comparable: which technologies are they MCS-certified for, will they survey before quoting, and what SCOP are they designing for. Our seven questions to ask guide covers the full list. If an installer pushes one technology without discussing your property's specific constraints, garden size, water access, outdoor wall space, that's worth a second opinion before committing.

How the BUS grant changes the calculation

Before the £7,500 grant, ground and water source's higher efficiency had to justify a much bigger capital gap over air source. With the grant applying equally across ASHP, GSHP and WSHP, the gap between net costs narrows considerably, ASHP typically nets to £2,500 to £6,500, GSHP to £10,500 to £27,500. That's still a meaningful difference, but it means the decision is less about "can I justify the extra spend" and more about "does my property actually have the garden, water access or budget for the alternative". For most semi-detached and terraced properties without unusual site constraints, that question answers itself in favour of air source.

When it's worth getting more than one type quoted

Even if ASHP is the obvious default, it's worth getting a second quote for an alternative technology when your property sits near a genuine decision boundary: a rural property with a large garden and no mains gas is a case where GSHP deserves a real look alongside ASHP, not just a rejected afterthought. Similarly, a new-build with MVHR already specified is worth comparing EAHP against ASHP before the design is locked in. For most other properties, a second technology quote mostly confirms that ASHP was the right call rather than changing the outcome, but it costs nothing to ask.

Keeping an open mind between similar-looking options

It's easy to anchor on the first technology an installer mentions, but a genuinely independent comparison means asking what a second installer, ideally one who does a different mix of technologies, would recommend for the same property. Installers naturally quote more confidently in the technology they do most often, which isn't the same as it being objectively best for your specific site. Use the decision tree above as your own starting filter before any conversation, so you can spot if a recommendation doesn't match your property's actual constraints.

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