Air Source vs. Ground Source Heat Pumps: What’s the Difference, and Which Is Best for You? (2025 Guide)
As the world moves toward cleaner, more efficient heating solutions, heat pumps have quickly become the frontrunners for homeowners and businesses alike. Among the most popular options are Air Source Heat Pumps (ASHPs) and Ground Source Heat Pumps (GSHPs)—two technologies that work on the same principle but differ significantly in installation, cost, efficiency, and long-term value.
If you’re trying to decide between them, this comprehensive guide breaks down how they work, the key differences, costs, benefits, drawbacks, and which type is best for your home or project. By the end, you’ll have a clear picture of which system offers the best return for your climate, budget, and energy goals.
What Are Heat Pumps, and Why Are They So Efficient?
Heat pumps operate on a simple but powerful concept: they transfer heat instead of generating it.
Both air source and ground source systems use electricity to extract heat from the environment—either the air or the ground—and move that heat into your home. In summer, they reverse the process and act like air conditioners.
Because they move heat rather than create it, heat pumps are 3 to 5 times more energy-efficient than traditional boilers or electric heaters.
What Is an Air Source Heat Pump (ASHP)?
An Air Source Heat Pump extracts heat from the outdoor air and transfers it into your property through a refrigeration cycle. Even when temperatures drop below freezing, the system can still absorb heat from the air.
Types of ASHPs
- Air-to-Water Heat Pumps: Provide heating and hot water; compatible with radiators and underfloor heating.
- Air-to-Air Heat Pumps: Provide warm or cool air through vents; do not produce hot water.
How ASHPs Work
- The outdoor unit draws in air.
- Refrigerant absorbs heat and is compressed.
- Compressed refrigerant heats water or air in the indoor system.
- Heat is distributed through radiators, fan coils, or underfloor heating.
Key Features of ASHPs
- Easiest heat pump type to install.
- Lower upfront cost than GSHPs.
- Suitable for most homes without major renovations.
What Is a Ground Source Heat Pump (GSHP)?
A Ground Source Heat Pump, also known as a geothermal heat pump, extracts heat from the ground via underground pipe loops filled with a heat-transfer fluid.
The ground maintains a stable temperature year-round (generally 10–12°C in many regions), making GSHPs highly efficient—even in harsh winters.
Types of GSHP Loop Systems
- Horizontal loops: Pipes laid in trenches 1–2 meters deep
- Vertical loops: Boreholes drilled 50–200+ meters deep
- Pond/lake loops: Pipes submerged in a body of water
How GSHPs Work
- Fluid circulates through underground loops, absorbing stable ground heat.
- A heat pump compresses the fluid, increasing the temperature.
- Warmth is transferred into the home’s heating system.
- The cooled fluid returns underground to repeat the cycle.
Key Features of GSHPs
- Highest possible heating efficiency.
- Long lifespan (up to 50 years for underground loops).
- Requires land or drilling capacity.
Key Differences Between Air Source and Ground Source Heat Pumps
Below is a clear comparison of the major differences that homeowners care about most.
A. Efficiency
Air Source Heat Pump
- Efficiency varies with outdoor temperature.
- Can struggle slightly in extreme cold without backup heating.
- Typical COP (Coefficient of Performance): 2.5–3.5
Ground Source Heat Pump
- Efficiency remains stable year-round due to consistent ground temperature.
- Excellent performance in cold climates.
- Typical COP: 3.5–5
Winner: Ground Source — consistently higher efficiency and lower running costs.
B. Installation Cost
Air Source
- Lowest installation cost.
- No drilling or ground excavation required.
- Typical cost: £7,000–£14,000 (varies by country and size).
Ground Source
- Costs can be significantly higher.
- Requires either a large land area or expensive borehole drilling.
- Typical cost:
- Horizontal loops: £14,000–£25,000
- Vertical boreholes: £25,000–£45,000+
Winner: Air Source — far more affordable upfront.
C. Running Costs
Air Source
- Efficient but more impacted by weather changes.
- Higher energy usage in colder months.
- Annual running cost: Moderate.
Ground Source
- Most efficient heating type available.
- Lower yearly energy bills.
- Annual running cost: Low.
Winner: Ground Source — lower long-term operating costs.
D. Space Requirements
Air Source
- Requires only an exterior wall or ground space for the outdoor unit.
- Suitable for urban homes and small plots.
Ground Source
- Needs significant land for horizontal loops — typically 2–3 times the heated floor area.
- Vertical boreholes solve land issues but increase cost substantially.
Winner: Air Source — ideal for limited space.
E. Lifespan and Maintenance
Air Source
- The outdoor unit is exposed to the weather.
- Lifespan: 15–20 years.
- Occasional maintenance is required (cleaning, refrigerant check).
Ground Source
- Underground pipes last 50–100 years.
- An indoor heat pump typically lasts 20–25 years.
- Very low maintenance once installed.
Winner: Ground Source — long-lasting and extremely reliable.
F. Noise Level
Air Source
- An outdoor fan produces noticeable sound.
- Modern units are quieter but still audible.
Ground Source
- Very quiet—no outdoor fan.
Winner: Ground Source — best option for noise-sensitive areas.
Pros and Cons of Air Source Heat Pumps
Advantages
- Lower upfront cost.
- Quick and simple installation.
- Works well in most climates.
- Suitable for retrofitting older homes.
- Compact footprint.
Disadvantages
- Lower efficiency in extremely cold weather.
- Requires an outdoor unit (visible and noisy).
- Higher running costs compared to GSHPs.
- Shorter lifespan.
Pros and Cons of Ground Source Heat Pumps
Advantages
- Highest efficiency available.
- Extremely low operating costs.
- Long lifespan (especially for ground loops).
- Silent operation.
- Stable performance in all climates.
Disadvantages
- High upfront installation cost.
- Requires land for trenches or expensive drilling.
- Longer installation time.
- Planning permits may be required depending on the location.
Which Heat Pump Is Better for My Home?
Below are the scenarios in which each system is the clear winner.
Choose an Air Source Heat Pump If:
- You want the lowest upfront cost.
- You live in a mild or moderate climate.
- You lack land or cannot drill boreholes.
- You need fast installation.
- You are retrofitting a property with limited space.
Choose a Ground Source Heat Pump If:
- You want maximum efficiency and the lowest long-term bills.
- You live in a cold climate.
- You plan to stay in your home long-term.
- You have land for horizontal loops or a budget for deep drilling.
- You are building a new home (ideal scenario).
Cost Comparison Summary
| Category | Air Source Heat Pump | Ground Source Heat Pump |
| Upfront Cost | £7k–£14k | £14k–£45k+ |
| Efficiency | Moderate | Very High |
| Running Costs | Moderate–Low | Very Low |
| Lifespan | 15–20 years | 20–25 years (up to 100 for loops) |
| Climate Performance | Good | Excellent |
| Noise | Moderate | Near Silent |
| Suitable For | Most homes | Homes with land or new builds |
Environmental Impact: Which Is Greener?
Both ASHPs and GSHPs use renewable energy, drastically reducing carbon emissions over gas or oil heating.
However, GSHPs’ higher efficiency means they:
- Use less electricity over time
- Produce lower annual carbon emissions.
- Reduce strain on the electrical grid.
If environmental impact is your top priority, ground source is the most sustainable option.
Incentives and Rebates
Many countries offer incentives for heat pumps, such as:
- Government grants
- Tax credits
- Low-interest green loans
- Renewable heat incentives
These programs can reduce the cost of installation dramatically—sometimes by 30–60%.
Both ASHPs and GSHPs are usually eligible, but policies vary. Always check your local energy authority for the latest incentives.
Final Verdict: Which One Should You Choose?
There is no one-size-fits-all answer, but here is the simplest way to decide quickly:
Choose Air Source if you want:
- Lower upfront cost
- Quick installation
- Suitable for smaller properties
- Good performance at a reasonable price
Choose Ground Source if you want:
- Maximum efficiency
- Lowest lifetime costs
- Silent operation
- Best performance in cold climates
- A long-term, future-proof solution
If budget and land allow, ground source heat pumps are the superior system in most technical categories. However, air source heat pumps are the best choice for most homeowners due to flexibility, affordability, and ease of installation.
FAQ: Air Source vs. Ground Source Heat Pumps
1. Are ground-source heat pumps always more efficient than air-source?
Generally, yes. Ground source heat pumps maintain higher efficiency because the ground temperature remains stable year-round, unlike outdoor air. This means GSHPs deliver better performance in winter and lower running costs.
2. Do heat pumps work well in very cold climates?
Both types work in cold climates, but ground source heat pumps perform better because they use the earth’s stable heat. Modern air source systems can also operate efficiently in freezing temperatures, but may see reduced performance and require more electricity.
3. How long do heat pumps last?
- Air Source Heat Pumps: 15–20 years
- Ground Source Heat Pumps: 20–25 years
- Ground loops (underground pipes): 50–100 years GSHPs offer the longest overall system lifespan.
4. Do heat pumps require underfloor heating?
No, but they perform best with low-temperature heating systems such as underfloor heating or oversized radiators. Standard radiators can work, but efficiency may be slightly lower.
5. How noisy are air source heat pumps?
ASHPs have a fan and compressor, so they produce a noticeable but generally quiet outdoor hum—similar to an air conditioner. GSHPs are nearly silent because no outdoor fan is needed.
6. Can I install a ground source heat pump if I don’t have much land?
Yes, if you opt for vertical boreholes instead of horizontal trenches. However, drilling can increase installation costs significantly.
7. Are heat pumps expensive to run?
Compared to gas, oil, or electric resistance heating, heat pumps are much cheaper to operate. GSHPs offer the lowest running costs, while ASHPs are still highly efficient and economical.
8. Do heat pumps also provide cooling?
Yes. Most air source heat pumps can reverse operation and provide cooling in summer. Ground source systems can also cool homes, often with extremely high efficiency.
