Air Source Heat Pumps vs. Ground Source Heat Pumps

Heating is a lifesaver during the winter, both literally and figuratively. Without the burst of heat, getting out of bed in the mornings would be impossible, and clothes would never dry without a tumble dryer. Today, we are turning to renewable heat sources for this lifesaver, bringing a common debate on ground vs air source heat pumps.

With energy prices increasing, people are more conscious than ever about their energy consumption and are trying to find alternative methods to heat their properties. Air Source Heat Pumps (ASHPs) and Ground Source Heat Pumps (GSHPs) are alternative options that are gaining popularity.

But which one is better for you? Using our 30+ years of experience in the heating, ventilation and air conditioning industry, we compare GSHP vs ASHP, exploring both types of heat source pumps.

Ground vs Air Source Heat Pumps: How They Work

The first comparison of ground vs air source heat pumps is on how they work.
Air source heat pumps (ASHPs) work like magic heaters or coolers for your home. Imagine them as devices that can utilise warmth from the outdoor air, even when it's chilly. Using a special liquid, these pumps grab the outdoor heat and turn it into a hot gas by squeezing it. This hot gas then goes inside your property and gives off its warmth, making your home a comfortable temperature.

They are also able to work in reverse. In the warmer months, they can flip and act as coolers, taking away the heat from the inside and sending it outside. So, whether it's winter or summer, these handy pumps are temperature control experts, making sure your home stays just the temperature you like it.

On the other hand, ground source heat pumps work underground. They have loops buried in the floor outside, which, in the winter, soak up the warmth from the Earth and use it to warm up your home. When summer hits, they reverse the trick, taking the heat from your home and sending it back to the cool underground, giving you a cooler space.

Installation and Location

Installation of a GSHP vs ASHP is more complex.
Installing an ASHP can be fairly easy and usually only takes 2-5 days. There are several stages to ASHP installation once a system has been designed and agreed upon.

Indoor installation, where the indoor unit, which includes the heat exchanger and fan, is installed. This unit is responsible for releasing the heat generated into the indoor space. Typically, these units will go in a plant room, utility room, garage or airing cupboard.
We will move on to outdoor installation, where the outdoor unit, comprising the compressor and coils, is positioned. This unit extracts heat from the outdoor air during the heating mode and releases heat during the cooling mode.
With units in place, the refrigerant pipes and electrical wiring will be connected between the indoor and outdoor units to facilitate the transfer of heat and the operation of the ASHP.
The control system, which manages the operation of the ASHP, is installed. This may include a thermostat or a more advanced control interface for adjusting settings.

While installing a GSHP follows a similar installation process, it is slightly more complex as it involves getting pipes into the ground.

Once the design is signed off, the ground loop, a system of pipes filled with heat-transfer fluid, is installed in the ground. This is done using one of three methods;
Horizontal Loop, buried in trenches:
Vertical Loop: drilled deep boreholes, or
Slinky/Coiled Loop: buried in a horizontal slinky pattern.
Our installation teams will then install the indoor unit, including the heat exchanger and pump, which extract heat from the ground loop during the heating mode and release heat during the cooling mode.
Refrigerant pipes and fluid pipes connect the indoor unit to the ground loop, enabling the transfer of heat between the ground and the heat pump system.
The control system will be installed, including a thermostat or control interface.

GSHP vs ASHP: Efficiency and Performance

The efficiency of ASHPs and GSHPs is commonly measured by the Coefficient of Performance (COP) and the Seasonal Performance Factor (SPF). These values provide insights into how effectively each type of heat pump can convert electricity into heat over time.

The coefficient of performance measures how much heat is pumped out compared to the energy used. This measurement can vary based on factors like outdoor temperature, system efficiency, and the specific model.

So what is the COP for ground vs air source heat pumps?

The COP for an ASHP typically ranges from 2.5 to 4. This means that for every unit of electricity consumed, the heat pump produces 2.5 to 4 units of heat.

Meanwhile, the COP for a GSHP is generally higher, as they typically range from 3 to 5 or more. This is because the consistent temperature of the ground allows these systems to achieve higher efficiencies, especially in colder climates.

The SPF takes into account the performance of ASHPs and GSHPs across an entire heating season, considering temperature variations throughout that period.

ASHPs typically have SPF values between 2 and 3.5, depending on factors like climate, system design, and user behaviour.

Again, GSHPs tend to have higher SPF values than ASHPs, with SPF values for GSHPs commonly ranging from 3 to 5 or higher. Similar to the COP, a stable ground temperature contributes to a more consistent performance throughout the year.

Operating Costs

When it comes to comparing the cost of a ground vs air source heat pump, both have their own considerations.
ASHPs, being more common and budget-friendly upfront, tend to have lower installation costs. However, their efficiency may fluctuate with outdoor temperatures, impacting overall operating expenses.

GSHPs, on the other hand, boast higher installation costs due to the ground loop system, but their stable efficiency, especially in colder climates, can translate to lower long-term operating costs.

Ground vs Air Source Heat Pumps: Environmental Impact

The environmental impact of these heat sources is another element to the comparison of ground vs air source heat pumps.
Both ASHPs and GSHPs are champions in reducing carbon footprints. ASHPs are incredibly eco-friendly as they use the outdoor air as their power source to efficiently heat and cool homes. While they may require electricity, advancements in renewable energy sources are making their operation increasingly green.

On the other side of the green spectrum, GSHPs tap into the stable ground temperature, offering an even more consistent and sustainable performance. They may have a higher initial carbon footprint due to the ground loop installation, but over time, their energy efficiency and minimal environmental impact shine through.

Which Is Right for You: GSHP vs ASHP

Choosing a heat pump is down to personal preference, but there are a few things that you will need to consider when making the choice.

What considerations should you make in the decision of ground vs air source heat pump?

While GSHPs appear to have better performance due to the stable temperature of the ground, they need ground space, so if you don't have the space for them, they aren't suitable for your home. An ASHP is more likely to be suitable for any residential home as the units can be installed within the home and attached to the house building.

You will also need to consider the cost of running and installation. ASHPs are cheaper to install but due to the installation process being more complicated, the initial cost of a GSHP is more expensive.

When it comes to factors of environmental impact, once installed, both of these heating sources use renewable energy, so have minimal impact on the environment.

Speak To Our Experts

The team at Meridian Cooling are always happy to answer any questions you might have and discuss which one might be suitable for your home.

Call us to start a conversation about GSHP vs ASHP.

If you are interested in installing an air source heat pump or ground source heat pump, get a quote online or call our friendly team on 01202 658254.