Making the switch to renewable heating is a significant decision for any homeowner. As heat pump specialists in Chippenham, one of the most common questions we receive is whether an air source or ground source heat pump is the better option. Both systems offer excellent efficiency and environmental benefits, but they have distinct differences that make each more suitable for different properties and circumstances.
Understanding the Different Systems
Before comparing the options, let’s clarify how each system works:
Air Source Heat Pumps (ASHPs):
- Extract heat from outdoor air, even in cold temperatures
- Typically installed on an external wall or free-standing on the ground
- Require minimal outdoor space
- Connect to your home’s heating distribution system (radiators or underfloor heating)
- Can provide space heating and hot water
- Operate at slightly lower efficiencies in very cold weather
Ground Source Heat Pumps (GSHPs):
- Extract heat from the ground via buried pipes (ground loops)
- Require significant outdoor space for horizontal loops or boreholes for vertical loops
- Internal unit similar in size to a large fridge
- Connect to your home’s heating distribution system
- Provide consistent performance regardless of outdoor air temperature
- Typically achieve higher efficiencies than air source systems
Installation Considerations
Air Source Heat Pump Installation:
- Minimally invasive installation requiring no groundworks
- External unit mounted on a wall or concrete base
- Typically takes 2-3 days to install
- No planning permission usually required (under permitted development in most cases)
- Can be installed in almost any property with sufficient external space for the unit
Ground Source Heat Pump Installation:
- Requires significant groundworks for burying collector loops
- Horizontal loops need 200-300% of your heated floor area in garden space
- Vertical boreholes require less surface area but are more expensive to drill
- Installation typically takes 5-10 days, depending on the groundworks
- More disruptive installation process
- Planning permission may be required in some circumstances
Performance and Efficiency
Air Source Heat Pump Performance:
- Coefficient of Performance (COP) typically 3.0-4.0 (produces 3-4 units of heat for every unit of electricity)
- Seasonal Performance Factor (SPF) around 2.8-3.5 in UK climate
- Performance varies with outdoor temperature
- Slightly noisier operation (comparable to a modern fridge)
- Typically 20+ year lifespan with proper maintenance
Ground Source Heat Pump Performance:
- COP typically 3.5-4.5
- SPF around 3.2-4.0 in UK climate
- Consistent performance year-round regardless of weather
- Near-silent operation
- 25+ year lifespan for the heat pump unit (ground loops can last 50+ years)
Cost Comparison
Air Source Heat Pump Costs:
- Lower initial installation: £8,000-£13,000 before grants
- Eligible for £7,500 Boiler Upgrade Scheme grant
- Lower installation costs but slightly higher running costs
- Simpler and less expensive maintenance
- Net cost after grant: £500-£5,500
Ground Source Heat Pump Costs:
- Higher initial installation: £15,000-£35,000 before grants
- Eligible for £7,500 Boiler Upgrade Scheme grant
- Higher installation costs but lower running costs
- More complex system with potentially higher maintenance costs
- Net cost after grant: £7,500-£27,500
Space Requirements
Air Source Heat Pump Space Needs:
- External unit dimensions approximately 1m x 1m x 0.5m
- Requires good airflow around the unit
- Minimal distance from property boundaries (usually 1m)
- No ground space required if wall-mounted
- Suitable for most properties including those with limited outdoor space
Ground Source Heat Pump Space Needs:
- Horizontal loops require 200-300% of heated floor area
- Typical three-bedroom house needs 300-500m² of garden
- Boreholes require less surface area but need access for drilling equipment
- Internal unit similar in size to a large fridge/freezer
- Not suitable for properties with very limited outdoor space
Ideal Applications
Air Source Heat Pumps Are Ideal For:
- Properties with limited outdoor space
- Urban or suburban homes
- Retrofit projects where minimal disruption is preferred
- Properties where lower upfront cost is a priority
- Homes where the heating system is being upgraded incrementally
Ground Source Heat Pumps Are Ideal For:
- Properties with large gardens
- New build projects where groundworks are already taking place
- Homeowners prioritising long-term efficiency over initial cost
- Rural properties with ample land
- Situations where noise might be a concern
- Properties in very cold areas where ASHPs might struggle during extreme weather
Environmental Impact
Both systems significantly reduce carbon emissions compared to fossil fuel heating, but there are some differences:
Air Source Heat Pumps:
- Lower embodied carbon due to simpler installation
- Slightly lower efficiency means marginally higher operational emissions
- Refrigerant with higher global warming potential (being addressed in newer models)
Ground Source Heat Pumps:
- Higher embodied carbon due to extensive groundworks
- Higher efficiency means lower operational emissions over time
- Smaller refrigerant charge with lower leakage risk
Making Your Decision
When deciding between air source and ground source heat pumps, consider these questions:
- How much outdoor space do you have available?
- What’s your budget for both installation and running costs?
- How important is absolute efficiency vs. cost-effectiveness?
- Are you concerned about visual impact or noise?
- How long do you plan to stay in your property?
- Is minimising disruption during installation important?
For most UK homeowners, air source heat pumps offer the most practical and cost-effective solution due to their lower installation costs, minimal space requirements, and good efficiency. However, ground source systems can be the better long-term investment for properties with sufficient land and where higher upfront costs can be accommodated.
Expert Guidance for Your Home
Every home is unique, and the best heat pump solution depends on numerous factors specific to your property and requirements. Our team of experienced heat pump installers in Chippenham can provide a detailed assessment and personalised recommendations.
Contact us today for a free consultation and quote tailored to your specific heating needs. With the right system, you can enjoy efficient, environmentally friendly heating regardless of which technology you choose.
