Air Source vs Ground Source Heat Pumps
Air source and ground source heat pumps both qualify for the full €12,500 SEAI grant, but they differ on install cost, efficiency, and the space a property needs. Ground source runs roughly 20% more efficiently and costs €4,000 to €10,000 more to install.
Air-to-Water vs Ground-Source, Compared
| Attribute | Air-to-water | Ground-source |
|---|---|---|
| Installed cost | €9,000–€18,000 | €15,000–€30,000 |
| Real-world SCOP, Irish conditions | 2.8–3.5 | 3.5–5.0 |
| Running cost vs air-to-water | Baseline | ~20% lower |
| Heat source | Outdoor air | Buried loop or borehole, ground stays 10–12°C year-round |
| Space needed | Small outdoor unit | Garden space for loops, or borehole access |
| Max SEAI grant | €12,500 | €12,500 |
| Best suited to | Most Irish homes | Larger rural properties with land |
Ireland’s mild winters, averaging 4 to 7°C, narrow the efficiency gap between the two compared to colder climates. For a typical 3-bed semi, the running-cost saving from ground source is often modest in absolute terms, roughly €100 to €400 a year, and doesn’t fully offset the higher upfront cost within a typical ownership period.
Air-to-Water Heat Pumps
Air-to-water heat pumps extract heat from outdoor air and transfer it into a wet central heating system, radiators, underfloor heating, and a hot water cylinder, using a refrigerant cycle and an outdoor compressor unit.
Works well when
- Standard semi-detached or estate home
- Limited garden space
- Budget is a primary factor
Trade-offs
- Slightly lower efficiency than ground source
- Outdoor unit produces some operational noise
- Radiators often need upsizing
Ground-Source Heat Pumps
Ground-source heat pumps draw heat from buried pipework circulating a water and antifreeze mixture, either a horizontal loop trenched across a garden or a vertical borehole, exploiting Ireland’s stable 10 to 12°C year-round ground temperature.
Works well when
- Larger rural property with garden space
- New build with room for ground loops
- Noise-sensitive site
- Planning to stay long-term to recover the extra cost
Trade-offs
- Meaningfully higher upfront cost
- Requires significant groundworks
- Longer installation timeline than air source
Air-to-Air Heat Pumps
Air-to-air heat pumps extract heat from outdoor air and blow warm air directly into rooms through wall-mounted indoor units, without connecting to a wet heating system or a hot water cylinder.
Water-Source Heat Pumps
Water-source heat pumps extract heat from a well, pond, lake, or other water body on or near the property, using it as the heat exchange medium instead of air or ground.
Which One Fits a Given Property
Air Source vs Ground Source Questions
Which is more efficient, air source or ground source?
Ground source, with a real-world SCOP of 3.5 to 5.0 against air-to-water’s 2.8 to 3.5, roughly a 20% running-cost advantage.
Is ground source worth the extra cost in Ireland?
Often not for a typical suburban home. Ireland’s mild winters narrow the efficiency gap, and the annual saving, roughly €100 to €400, takes years to offset a €4,000 to €10,000 higher install cost. It suits larger rural properties better.
Can air-to-air heat pumps get the full SEAI grant?
No. Air-to-air is capped at €7,500 since the grant’s heating-upgrade component doesn’t apply, there are no radiators to upgrade.
Do I need planning permission for a heat pump?
An air source outdoor unit is generally classed as permitted development in Ireland. Exceptions can apply depending on the property, an installer confirms this during survey.
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