Heat pumps are energy-efficient and renewable energy heating and cooling systems. Heat pumps work completely opposite to traditional heating systems which generate heat using fossil fuels or electric resistance. Heat pumps work by transferring heat from one place to another which makes them highly efficient and lowers the carbon footprint. 

There are different types of heat pumps available that source heat from different sources such as air, water, and ground. This guide compares two main types of heat pumps air source and ground source.  This will help you make an informed decision on which one might be suitable for your home heating requirements. 

Stick to this guide as we dig deeper into the comparative analysis of air-source heat pumps and ground-source heat pumps. 

 What are Heat Pumps? How Do They Work?

Heat pumps are energy-efficient devices that use a refrigeration cycle to transfer thermal energy or heat from one place to another. Using renewable energy sources, they can provide both heating and cooling to buildings to reduce energy costs, and carbon dioxide emissions, and help combat fuel poverty. 

Heat pumps use electricity to extract heat from low-temperature sources such as outside air or ground and transfer it to high-temperature areas. Heat pumps mainly consist of four main components, which are the evaporator, compressor, condenser, and expansion valve. All these components help the heat pumps work which is absorbing heat from a source, raising its temperature, releasing the heat into the property, condensing refrigerant to liquid, and reducing the pressure of the refrigerant to cool it down. 

Type of Heat Pumps

There are two major types of heat pumps, each with a different functionality and purpose. 

1. Air-Source Heat Pumps (ASHPs)
2. Ground-Source Heat Pumps (GSHPs)

Below, we will be comparing both types of heat pumps in detail. 

Air-Source Heat Pumps (ASHPs)

As the name suggests, air-source heat pumps extract heat from outside air and transfer it indoors to provide heating and hot water, even in lower temperatures. Its working principle is simple as it absorbs heat from the air and passes it through a compressor to increase its temperature. This heated air is then transferred to radiators and underfloor heating.

Air source heat pumps have two main types:

• Air-to-Air Heat Pumps: Air-to-air heat pumps transfer heat directly to the indoor air to heat the space and then use ducted air systems to distribute the heated air to heat space and water. 
• Air-to-Water Heat Pumps: Whereas air-to-water heat pumps transfer the extracted heat to water which is then circulated through radiators and underfloor heating systems. These pumps, along with providing heat, can provide hot water for domestic use. 

Benefits of Air Source Heat Pumps

To compare both systems, it is important to know the unique benefits both bring to households. Below are the advantages of using air-source heat pumps for your heating requirements:

• Lower Upfront Costs: Air-source heat pumps have lower upfront installation costs. Typically, an air source heat pump’s installation ranges from £8000 to £12000 which is way cheaper than ground source heat pumps. 
• Number of Grants Available: ASHPs can be installed with minimum or zero costs with plenty of air source heat pump grants available for this heating improvement under ECO4 and other government grants. 
• Energy Efficiency and Savings: Air-source heat pumps have a COP (coefficient of Performance) ranging from 3 to 4 units of heat on spending one unit of electricity, which reduces energy costs significantly. 
• Low Maintenance Requirements: Air-source heat pumps can perform well with just the annual servicing and do not require further maintenance or extra repairs to keep your heating systems running. 

Challenges:

As far as the challenges associated with air-source heat pumps are concerned, the major challenge one can face is it reduces its performance in baltic weather conditions. So, if you live in an area of the UK with extreme weather conditions, air-source heat pumps might not be a great option for you. 

Ground-Source Heat Pumps (GSHPs)

Ground source heat pumps extract heat from the ground to provide heating and hot water to households. These devices benefit from relatively lower earth temperatures in the UK, usually 10-12°C. Because the earth's temperature remains constant, it does not affect the performance of heat pumps. No matter what the weather conditions are they perform adequately.

Ground source heat pump works in three simple steps, heat extraction, compression, and distribution. This heating system has two types of ground loop systems, vertical and horizontal loop systems. The selection of these systems is subject to outdoor space, limited space requires vertical loops, which involves drilling boreholes. 

Benefits of Ground Source Heat Pumps

Here are the common and most useful advantages of ground-source heating systems:

• Higher Efficiency: the energy efficiency is higher with ground source heating systems. It saves approximately 70% on heating costs as compared to traditional systems. 
• Stable Performance: Because these systems extract heat from the ground, which has a stable temperature of 10-12°C in the UK, ground source heat pumps provide stable heat and do not reduce heat in baltic weather conditions. 
• Low Maintenance: same as air-source heat pumps, ground-source heat pumps are also low maintenance and perform well with annual servicing only. 

Challenges:

The major challenge involved with ground source heat pumps is higher upfront costs which may range from £15,000 to £30,000. Plus, there is less government funding available for ground-source heat pump installations as compared to air-source heat pumps. 

Another challenge you may face is if you have limited outdoor space, you might need grilling boreholes in your property leading to property damage and additional costs. 

Comparative Analysis Table of ASHPs and GSHPs

The below table demonstrates the comparative analysis and main differences between air-source and ground-source heat pumps. 

Feature

Air-Source Heat Pumps

Ground-Source Heat Pumps

Efficiency & Performance

COP 3-4 (drops performance after -5°

COP 4-5 (Provides Constant Performance 

Installation Costs

£8,000–£12,000

£15,000-£30,000

Running Costs 

Higher then GSHPs 

Lower energy costs

Annual Maintenance Cost

£100–£150

£150–£200

Lifespan

15-20 years 

20-25 years 

Government Grants

ECO4 (fully funded) & BUS Scheme (partially funded) 

BUS scheme (Partially Funded) 

Final Thoughts

To wrap up the discussion, ground source and air source heat pumps are energy-efficient and renewable energy heating systems. Both have their own benefits and drawbacks to cater for. Air-source heat pumps are not suitable for extremely cold weather conditions and drop performance, while ground-source heat pumps provide stable performance. 

Air-source heat pumps have lower upfront costs and have various grants available, while ground-source heat pumps have limited grants available with higher upfront costs. By providing this information, we have made it possible for you to make an informed decision as per your energy requirements.