Summary

The choice between air source and ground source heat pumps is rarely close to 50/50 in practice — for the large majority of UK domestic retrofits, ASHP wins on cost and disruption, and GSHP is reserved for specific situations: new-build properties where groundworks are happening anyway, rural properties with generous garden space, or sites where outdoor unit noise is a hard constraint (tight urban plots, listed buildings, noise-sensitive neighbours).

Both technologies extract heat from a naturally-renewing source using a vapour-compression refrigeration cycle and both are covered by the same government grant scheme, but the economics diverge sharply once groundworks enter the picture. This guide sets the two head-to-head across the factors that actually decide the choice for a tradesperson advising a customer: upfront cost, running cost and efficiency, land and garden requirements, grant eligibility, planning permission, and suitability by property type.

This is a decision-support comparison, not an installation guide for either technology — for ASHP installation detail see air source heat pump installation, and for GSHP loop sizing and installation detail see ground source heat pump installation.

Key Facts

Quick Reference Table

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Factor Air Source Heat Pump (ASHP) Ground Source Heat Pump (GSHP)
Typical installed cost (before grant) £7,000-£13,000 £19,000-£35,000+
BUS grant available £7,500 (£9,000 if replacing oil/LPG heating, from 21 Jul 2026) £7,500 (£9,000 if replacing oil/LPG heating, from 21 Jul 2026)
Typical COP ~3.0-4.0 ~4.0-5.0
Outdoor noise Audible outdoor unit; MCS Planning Standard assessment required None — no outdoor unit
Land/garden required Small footprint for outdoor unit only Large (horizontal loop) or borehole (small footprint, high cost)
Planning permission (typical domestic) Usually Permitted Development if MCS-compliant Usually no PD constraint (no outdoor unit); groundworks may need other consents
Disruption during install Low — outdoor unit + internal plumbing High — trenching or drilling across garden/site
Best suited to Most retrofit properties, terraced/semi housing, tight plots Rural/large-garden properties, new builds with planned groundworks
Lifespan of outdoor components ASHP unit typically 15-20 years Ground loop itself typically 50+ years; indoor unit similar lifespan to ASHP
Running cost Higher than GSHP for equivalent heat delivered Lower than ASHP for equivalent heat delivered, but higher capital cost extends payback

Detailed Guidance

Upfront Cost Comparison

The cost gap between the two technologies is driven almost entirely by groundworks, not by the heat pump unit itself — the indoor heat pump, cylinder, and hydraulic pipework cost is broadly comparable between an ASHP and GSHP installation of equivalent output. What separates them is that a GSHP needs either several hundred metres of trenched pipe or one or more boreholes drilled to 80-150m depth, both of which require specialist plant, labour, and time that an ASHP simply doesn't need — an ASHP outdoor unit sits on a small base and connects with a short pipe run.

This means the GSHP cost premium is highly site-specific. A property with easy, obstruction-free garden access for trenching machinery will pay less for its ground loop than one requiring borehole drilling because of limited space, or one where existing landscaping (patios, mature trees, drainage) has to be removed and reinstated around the trenches.

Running Cost and Efficiency

GSHP's efficiency advantage comes from a smaller temperature lift: the ground sits at a broadly stable 10-12°C year-round, while outdoor air temperature in the UK swings from around -5°C on the coldest winter nights to 25°C+ in summer. A heat pump has to work harder — and use more electricity per unit of heat delivered — the bigger the gap between its source temperature and the flow temperature it's producing. Because the ground rarely drops much below source temperature even in the depths of winter, GSHP maintains a relatively stable, efficient COP through the coldest UK weather, exactly when heating demand (and ASHP's relative efficiency disadvantage) is at its worst.

In practice this translates to GSHP running costs commonly 20-30% lower than ASHP for the equivalent heat delivered, but the far higher capital cost of the ground loop means the payback period on that running-cost saving is often very long — commonly cited in the range of 15-25+ years, well beyond what many homeowners consider when weighing the two options. See heat pump cop scop explained for how COP and SCOP are actually calculated and why real-world SCOP tends to undershoot the manufacturer-rated COP for both technologies.

Land and Garden Requirements

This is usually the single deciding factor in practice, before cost is even discussed. A horizontal ground loop needs roughly 8-10× the property's heated floor area in clear, obstruction-free land — trees, existing drainage, and buried services all rule out sections of garden, and the land can't be heavily paved or built over afterwards without disturbing the loop. For most suburban and urban plots in the UK, this simply isn't available.

Boreholes solve the space problem — a handful of 80-150m vertical bores in a relatively small footprint — but need a drilling rig with vehicle access, specialist GSHPA-accredited contractors, and carry a meaningful cost premium over horizontal trenching. See ground source heat pump installation for the full sizing methodology on both loop types.

An ASHP, by contrast, only needs a firm, level, well-ventilated spot for the outdoor unit with adequate clearance on at least two sides — achievable on the great majority of UK properties, including terraced housing with only a small yard or side passage.

Grant Eligibility (Boiler Upgrade Scheme)

Both ASHP and GSHP are eligible for the same Boiler Upgrade Scheme grant in England and Wales, currently a flat £7,500 (confirmed current as of September 2026, unchanged since October 2023; a temporary £9,000 rate applies only to homes replacing oil or LPG heating for applications from 21 July 2026). The grant is paid to the MCS-certified installer, who deducts it from the customer's invoice, and requires the installation to meet MCS 007 installation standards. Because the grant value is identical regardless of technology, it doesn't change the relative economics between ASHP and GSHP — it simply reduces both by the same amount, which in percentage terms benefits the cheaper ASHP installation more. See bus grant scheme guide for full eligibility criteria and the application process.

Planning Permission Differences

ASHP outdoor units in England commonly fall under Permitted Development, meaning no planning application is needed, provided the installation meets the conditions in Schedule 2, Part 14, Class G of the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended by the Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025) — including distance-from-boundary rules and the MCS 020 sound assessment requirement (37.0 dB(A) LAeq,5min, mandatory from 20 September 2025). Development is not permitted on a pitched roof, on a flat roof within 1m of the external edge, on a scheduled monument, or within a listed building; conditions can also vary for conservation areas and flats. See heat pump noise planning for the detailed planning and noise-distance rules.

GSHP largely sidesteps this issue because there's no outdoor unit generating the noise that triggers those PD conditions in the first place. However, the ground loop and any drilling works can raise separate considerations — trenching near boundaries, potential need to notify or consult the Environment Agency in edge cases (most domestic closed-loop systems fall below the abstraction licence threshold — see ground source heat pump installation), and, in some cases, local authority awareness of significant groundworks even where formal planning permission isn't required. Always check locally rather than assuming either technology is entirely permission-free.

Suitability by Property Type

Frequently Asked Questions

Is ground source always more efficient than air source in practice?

Generally yes, in terms of COP, because of the stable ground temperature — but "more efficient" doesn't automatically mean "better value." The far higher capital cost of GSHP means the running-cost saving takes many years to offset the extra install cost. For most retrofit customers without abundant land, ASHP delivers better overall value even though its COP is lower.

Can I install a ground source heat pump if I don't have a big garden?

Only via a borehole, which removes the large horizontal-loop land requirement but adds significant drilling cost and requires a GSHPA-accredited specialist contractor with rig access to the site. This can still make GSHP viable on a smaller plot, but the economics need checking carefully against ASHP for the same property.

Do both technologies qualify for the same government grant?

Yes — the Boiler Upgrade Scheme grant applies at the same rate to both ASHP and GSHP in England and Wales (£7,500, or £9,000 if replacing oil/LPG heating from 21 July 2026), provided the installation is carried out by an MCS-certified installer to MCS 007 standards.

Which is quieter — does that matter for planning permission?

GSHP has no outdoor unit and therefore no outdoor noise consideration at all. ASHP outdoor units are audible and their siting is governed by MCS Planning Standards noise assessment and, in England, Permitted Development distance-from-boundary conditions. Noise is rarely the sole deciding factor for most customers, but it can matter significantly on tight urban plots, close to neighbouring windows, or where a customer has had a bad experience with a noisy unit nearby.

Does either technology work well with an existing radiator system, or do I need underfloor heating?

Both ASHP and GSHP generally run at lower flow temperatures than a gas boiler, which can mean existing radiators need upsizing for the same room heat output — this applies to both technologies roughly equally, since the flow temperature question depends more on the property's heat loss and emitter sizing than on the heat source itself. See radiator sizing for heat pumps and heat pump sizing heat loss for the sizing methodology that applies to both.

Regulations & Standards