Heat Pump Comparison Guide
Air Source vs Ground Source Heat Pump: Which Is Right for UK Homes?
Choosing between air source and ground source used to be a compromise. Surface Thermal removes that choice.
Surface Thermal is best suited to projects where visual impact, shallow installation, or heritage constraints matter. If boreholes are not possible for your property, see our guide to ground source heat pump alternatives.
Comparison: Air Source vs Ground Source Heat Pumps and Surface Thermal
An at-a-glance overview of the key differences between renewable heating UK homes can choose from.
| Feature | Air Source (ASHP) | Ground Source (GSHP) | Surface Thermal |
|---|---|---|---|
| Noise Level | Audible outdoor unit | Silent (Outdoor) | Silent (Outdoor) |
| Visual Impact | Visible outdoor unit | None (underground) | None (under surfaces) |
| Boreholes Required | No | Yes (75-200m deep) | No |
| Outdoor Units | Yes | No | No |
| Installation Complexity | Low | High | Medium |
| Cold Weather Performance | Reduced efficiency | Consistent | Consistent |
| Thermal Yield (Winter Mean) | N/A (Air Temp Dependent) | 40-50 W/m² (Typical) | 55-57 W/m² (Sustained) |
| Best Suited Properties | Most properties | Large gardens/land | Properties with hardstanding |
Air Source Heat Pumps (ASHP)
How They Work
Air source heat pumps extract heat from the outside air using a refrigerant cycle, similar to a refrigerator running in reverse. Even when air temperatures are low, there is still heat energy that can be captured and upgraded for home heating.
The system uses an outdoor fan unit to draw air across a heat exchanger, where the refrigerant absorbs heat energy. This is then compressed to raise the temperature and transferred to your heating system.
Advantages
- • Lower upfront cost compared to ground source systems
- • Easier installation with minimal disruption to gardens
- • Suitable for most properties with outdoor space for the unit
- • Can provide cooling in summer months
- • Eligible for government grants under the Boiler Upgrade Scheme
Limitations to Consider
Noise Considerations
The outdoor fan unit produces audible noise during operation. While modern units are quieter than older models, noise can still be a concern for neighbours, particularly in terraced housing or quiet residential areas. Planning restrictions may apply.
Visual Impact
ASHPs require a visible outdoor unit, typically mounted on brackets or placed on a concrete base. This may not suit properties where aesthetics are a priority, particularly listed buildings or conservation areas.
Cold Weather Performance
Efficiency decreases as air temperatures drop. During the coldest UK winter days, the system works harder to extract heat, reducing its coefficient of performance (COP) compared to ground-based alternatives.
Planning Considerations
While often covered by permitted development rights, ASHPs may require planning permission due to noise output, distance from boundaries, or location in conservation areas.
Ground Source Heat Pumps (GSHP)
Borehole Systems
Vertical borehole systems drill deep into the ground, typically 75-200 metres, to access stable underground temperatures. Pipes filled with a water and antifreeze mixture circulate through these boreholes, absorbing ground heat.
Boreholes are suitable for properties with limited surface area but require specialist drilling equipment and geological surveys. Costs for drilling alone can range from £15,000 to £30,000+.
Horizontal Loop Systems
Horizontal ground loops are buried in trenches approximately 1-2 metres deep. They require significant land area, typically 2-3 times the floor area of the property being heated.
While cheaper than boreholes, horizontal systems cause major disruption to gardens and landscaping. They're most practical for new builds where installation happens before landscaping.
Advantages
- • Highest efficiency of traditional heat pump systems
- • Consistent performance regardless of air temperature
- • No visible outdoor units once installed
- • Very quiet operation
- • Long lifespan for ground loop components (50+ years)
Limitations
- • High installation costs due to drilling or excavation
- • Land requirements exclude many UK properties
- • Significant disruption during installation
- • Planning complexity for boreholes near water sources
- • Geological surveys required before installation
Surface Thermal (Teratherm)
A ground source heat pump alternative that captures thermal energy without boreholes and without outdoor units.
How It Works
Surface Thermal systems capture energy from three sources: solar radiation absorbed by the surface, ambient air temperature, and stable ground heat, all beneath driveways, patios, and other hardstanding areas.
The collector system is integrated invisibly into resin-bound surfaces during construction or renovation. No deep drilling or extensive excavation is required. Learn more about the technology behind Surface Thermal.
Verified Performance
Sustained Mean Yield
55-57 W/m²
GSENZH Verified Performance
Efficiency (SCOP)
4.4 SCOP
Continuous Winter Monitoring
Noise & Visual Profile
Silent (Outdoor)
No outdoor fan units or compressor noise
Winter Reliability
Zero Defrost Cycles
Unaffected by freezing air temperatures
Which Heat Pump Is Best for You?
The right choice depends on your property type, priorities, and circumstances. Here's a guide for different scenarios.
Urban Homes
Limited outdoor space and close neighbours
Surface Thermal is ideal, no outdoor unit noise, no boreholes, uses existing driveway or patio space. Air source may cause neighbour complaints. Ground source typically impractical without garden space.
Homes Without Gardens
Properties with driveways but minimal green space
Surface Thermal works perfectly with hardstanding surfaces. Traditional ground source requires extensive land. Air source is possible but adds visual clutter and noise.
New Builds
Construction projects with flexibility in design
All three systems can be integrated during construction. Surface Thermal can be installed as part of driveway/patio construction. Ground source trenches are easier before landscaping. Air source is quickest to add.
Renovation Projects
Upgrading existing heating systems
Air source offers the easiest retrofit. Surface Thermal is excellent if you're already replacing driveways or patios. Traditional ground source involves significant disruption to established gardens.
High-End Residential Properties
Premium homes where aesthetics matter
Surface Thermal provides invisible, silent operation perfect for luxury properties. Ground source is viable with large estates. Air source outdoor units may detract from property aesthetics.
Air Source vs Ground Source FAQs
Common questions about choosing between ASHP vs GSHP and ground source heat pump alternatives.