As the UK accelerates its transition away from gas heating, heat pumps are becoming a central solution for low-carbon buildings. But not all heat pumps are the same. Their physical layout, installation requirements, and achievable efficiency (COP) vary significantly. Choosing the right type depends on your site conditions, available land, and future energy strategy.
Below, we explore the three main types of heat pump—air-source, ground-source (horizontal loops), and borehole (vertical)—and assess the advantages, drawbacks, and real-world performance you can expect from each.
Before diving in, it’s worth remembering:
Any heat pump—regardless of source—needs a well-insulated building, low-temperature heating system, and adequate electrical capacity to perform effectively.
Often this includes upgraded radiators, improved pipework, and ensuring your electrical supply can handle a higher peak demand.
1. Air-Source Heat Pumps (ASHP)
How They Work
Air-source heat pumps extract heat from the outside air—even at sub-zero temperatures—and upgrade it to provide space heating and hot water.
Advantages
Lowest capital cost of all heat pump types.
Easiest installation: ideal for urban or constrained sites.
Good efficiency in UK climate, particularly the south and western regions.
Minimal disruption: only requires an outdoor unit and internal cylinder.
Disadvantages
Lower COP in cold weather, as outdoor air temperature falls.
Needs careful placement to manage sound levels and airflow.
Frost cycles can temporarily reduce output and efficiency.
Requires more electricity than ground or borehole systems on the coldest days.
Typical COP
Seasonal COP (SCOP): 2.5 – 3.5
Well-designed systems with low-temperature emitters can achieve 3.5+, especially in milder climates.
2. Ground-Source Heat Pumps – Horizontal Loops
How They Work
Pipes are buried in trenches 1–2 metres underground. The earth maintains a stable temperature, allowing the system to draw heat efficiently even in winter.
Advantages
Higher efficiency than air-source due to stable ground temperatures.
Very quiet operation: nothing above ground except manifolds.
Excellent for rural properties with sufficient land.
Disadvantages
Requires large land area: typically 2–3 times the heated floor area.
High excavation cost and significant ground disruption.
Performance depends on soil type and moisture content.
Not suitable for small plots or paved areas where reinstatement is costly.
Typical COP
Seasonal COP: 3.5 – 4.5
Moist, clay-based soil typically yields better performance than dry, sandy ground.
3. Borehole (Vertical) Ground-Source Heat Pumps
How They Work
Instead of trenches, deep boreholes (typically 80–200 metres) are drilled to access stable subsurface temperatures. Multiple boreholes can be combined for larger loads.
Advantages
Highest efficiency of all heat pump types due to deep, stable ground temperatures.
Minimal surface disruption after drilling—ideal for small plots.
Long working life for the ground loop—often 50+ years.
Excellent for commercial buildings with high or steady heat demand.
Disadvantages
Highest upfront cost—drilling is specialist and expensive.
Requires geological assessment, and unsuitable ground can increase costs.
Planning and logistics: drilling rigs need access and space.
Typical COP
Seasonal COP: 4.0 – 5.0
Systems with optimised flow temperatures (e.g., underfloor heating) can exceed 5.0 in the right geological conditions.
Insulation, Emitters, and Electrical Supply: The Non-Negotiables
Regardless of heat pump type:
1. The Building Must Be Well Insulated
If heat loss is too high, the pump will:
Run at higher temperatures,
Consume more electricity,
Deliver a lower COP.
Insulation, airtightness, and draft control are the cheapest “efficiency upgrades” available.
2. Heating Emitters Must Be Designed for Low Temperatures
Heat pumps perform best when delivering 35–45°C flow temperatures.
That often means:
Larger radiators,
Low-temperature fan coils, or
Underfloor heating.
Upgrading emitters is usually essential—especially when replacing a gas boiler.
3. Adequate Electrical Supply Is Required
Heat pumps can require:
upgraded consumer units,
dedicated electrical circuits, or
in some cases, a three-phase supply for larger properties.
Early checks during feasibility avoid expensive surprises.
Which Heat Pump Is Right for Your Building?
| Heat Pump Type | Best For | Key Benefit | Key Drawback |
|---|---|---|---|
| Air-Source | Homes and SMEs with limited space | Lowest cost | Lower efficiency in cold weather |
| Ground-Source (Horizontal) | Rural sites with land | Stable, high efficiency | Large land area needed |
| Borehole GSHP | Urban sites, commercial buildings | Highest COP and lifespan | Highest capital cost |
Final Thoughts
Selecting the right heat pump is about matching site constraints, budget, electrical capacity, and building fabric to the right technology. When designed and installed properly, all three system types can deliver excellent efficiency, significantly reduce carbon emissions, and provide low-carbon heating compatible with the UK’s net zero trajectory.
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