In order to solve the climate crisis, we need to electrify our heating and cooling. The question is hence not if we should install a heat pump, but whether it should be an air-source or a ground source one. In this chapter, we will shine light on different viewpoints and arguments in the air- versus ground-source discussion.
The elephant in the room
Before we delve into the benefits of having a ground source heat pump, let’s first address the elephant in the room: capital expenditure, or CAPEX.
Ground source heat pumps (GSHPs) have a reputation for being significantly more expensive than their air source (ASHP) counterparts, as you not only have to invest in the heat pump itself, but also in an expensive geothermal source. While it is true that GSHPs typically involve higher upfront costs, especially for single-family homes, this is not always the case.
- Increasingly, in neighbourhoods or city centres, strict noise regulations apply during certain hours. In some cases, the noise from an ASHP may require additional noise mitigation measures. These can be quite costly, particularly for larger projects, which reduces the difference in investment cost between the two systems, in favour of the ground source one.
- The largest portion of the investment is usually the geothermal system. For larger projects, or for fifth generation district heating, this system can be centralised, which lowers the investment cost for each individual user, as well as increasing the efficiency of the entire system.
That said, it can happen that, all things considered, a GSHP is not the cheapest solution. In your case, however, there are still numerous reasons to opt for a geothermal system over an air-source one.
Advantages of a ground source heat pump
The advantages of a ground source heat pump can be divided into two categories: individual reasons (why you, as a building owner, would choose a GSHP), and collective reasons (why we, as a society, should support the use of GSHPs). All the reasons are listed below, starting with the individual ones. The final two points, which concern the urban heat island effect and the issue of grid congestion, are collective reasons.
Higher efficiency
It is often said that GSHPs have a higher efficiency than ASHPs, and therefore have a lower operating cost. This reasoning is not entirely straightforward, so we will discuss the efficiency claim separately from the argument about operating costs, which is covered in the next section.
The efficiency of any heat pump is determined by the temperature lift. This refers to the temperature difference between the heat source (either the ground or the air) and the required supply temperature, which is typically between 35°C and 55°C. The greater this difference, the lower the efficiency. (This will be further discussed in Chapter 5.)
Since the ground temperature is usually higher than the air temperature (although this depends on the location), a ground source heat pump does indeed achieve higher efficiency. This higher ground temperature can be explained by the fact that the ground, in contrast to the outside air, is not simply used as a source of heat, but acts more like a heat battery. By storing heat in the ground during the summer months through cooling (as discussed further below), the ground temperature increases. This stored heat can then be used in winter to provide more efficient heating.
The higher efficiency of GSHPs is also reflected in the seasonal coefficient of performance, or SCOP, which is officially provided in all datasheets. In the past, the efficiency difference was quite significant, although today the gap has become smaller. However, a performance difference still remains, because heat transfer from a fluid to the refrigeration cycle inside the heat pump is easier than from air. Furthermore, ASHPs require a defrosting cycle, which also impacts performance, as discussed later.
In certain areas, such as cities or regions affected by climate change, the statement that the ground is on average warmer than the air does not always hold true. In practice, it is possible for an ASHP to achieve a higher average SCOP than a GSHP. However, this does not necessarily mean that it is cheaper to operate, as will be discussed now.
Operational cost
Nowadays, more and more electricity suppliers are moving away from a single, fixed electricity price towards dynamic tariffs, where the price can vary from hour to hour. This shift is driven by the increasing share of intermittent electricity sources, such as solar and wind energy.
Electricity prices tend to rise when demand is high but production is low. This typically occurs in winter, when there is limited sunlight and longer periods of low wind speed. During these colder conditions, an ASHP consumes more electricity than a GSHP, resulting in higher electricity costs.
In the milder periods of the year, such as spring and autumn, when the air temperature is similar to the ground temperature, the difference in efficiency between the two systems may disappear. However, since electricity prices are not critical during these periods, this becomes less relevant. Therefore, even if seasonal efficiency appears to be similar, the operational cost of a GSHP will be lower because its efficiency remains higher during the most critical and costly periods of the year.
Defrosting cycle
ASHPs extract energy from the air. However, when it is very cold outside, moisture in the air can freeze onto the heat exchanger, effectively blocking it. To prevent this, ASHPs have what are known as defrosting cycles. During these cycles, the unit periodically reverses its operation to heat up the heat exchanger and melt or evaporate any frozen moisture.
This defrosting process consumes electricity and can lead to significantly lower seasonal efficiency, especially in colder climates. Furthermore, during this defrosting cycle, the ASHP cannot supply heat to the building. Any heat demand during this period must therefore be met by a buffer tank, an electric resistance heater, or a backup ASHP in the case of larger systems.
Since GSHPs operate with a fluid in their primary circuit, this defrosting issue does not occur.
Effective cooling
We have already mentioned the advantages of having seasonal thermal energy storage when working with a GSHP for high efficiency heating, but it also is beneficial for the cooling performance.
First of all, geothermal borefields offer the possibility of using passive cooling. In this approach, no compression is required to achieve the cooling, since the cold geothermal fluid is used directly to cool the building. This results in what is often referred to as near-free cooling. In warmer climates, however, where the ground temperatures are rather high or the cooling demand is significant, it can be that passive cooling is just infeasible. In that case, it is also possible to rely on active cooling, where the compressor of the heat pump is used to provide the necessary cooling to the building.
The main difference is that, with a GSHP, this excess heat is not released into the environment, but is instead stored in the ground for use in winter. This creates a more efficient overall system. In addition, the efficiency of active cooling with a geothermal system is generally higher than with an air-based system, as ground temperatures are usually lower than ambient air temperatures during the cooling season.
Lifetime and maintenance
When calculating the total cost of ownership (TCO) for both an ASHP and a GSHP, it is important to take into account the expected lifetime and maintenance costs. ASHPs typically have a lifetime of between 15 and 20 years, whereas GSHPs can last for around 25 years.
The reason is straightforward. ASHPs are installed outdoors and are therefore exposed to various weather conditions, such as wind, snow, rain, and hail, which contribute to wear and tear. The repeated freezing and defrosting of moisture on the heat exchanger also accelerates material degradation, making this type of heat pump more prone to leaks. Additionally, when an ASHP is installed near the coast, the aggressive and corrosive air containing sea salt must be considered, as it can significantly shorten the system’s lifespan.
When this shorter lifetime is taken into account, the potentially higher initial cost of a GSHP becomes noticeably lower over time. Moreover, the geothermal part of the investment can easily last up to 50 years, provided it is accurately designed (as we will discuss in our next chapter).
Aesthetics and noise
Since GSHPs are installed entirely indoors, there is no visible unit outside the building. Although subjective, this often results in a more premium appearance. In addition to the aesthetic advantage, GSHPs are also quieter than air-source systems, as there is no fan required to move air over the heat exchanger. Over the years, ASHPs have become reasonably quiet, but if you live in a neighbourhood where many are in use, the sound can still be noticeable.
Urban heat island effect
The reasons above were individual ones: why should you, as a building owner, choose a GSHP? In addition to these personal benefits, there are also collective advantages, where choosing GSHPs is more beneficial for society as a whole than a widespread reliance on ASHPs. The issue of grid congestion will be discussed next, but first, let us focus on the urban heat island effect.
The urban heat island effect, as shown above, is the phenomenon where city centres and densely built neighbourhoods experience significantly higher temperatures than rural areas, with differences of up to 5 to 10 degrees Celsius on average. This is mainly due to materials such as concrete and road surfaces, which retain heat and gradually warm up the surrounding environment. Various sources of heat within the city, such as vehicles and heat pumps operating in summer, contribute further to this issue.
When every individual house owner installs an ASHP, the outside air will only increase in temperature, making summers even warmer and forcing your neighbours to also install a cooling system, making the outside air even warmer. In addition to that, since it is now warmer outside, more heat enters the building, so the ASHP has to work harder, pumping more heat into the environment. It is a negative, vicious cycle.
With (collective) GSHPs, this heat is not dumped into the environment, but stored in the ground. This can help balance the temperature swings in the outside air, since from summer to winter, only energy from the ground is used, instead of using the city air as a heat or cold dump.
Grid congestion
With the push towards electrification of our industries, transportation, and HVAC systems, the electricity grid is under considerable stress. Taking into account the intermittent nature of solar and wind electricity production, some regions may face congestion problems, where it is no longer possible to connect new buildings to the electricity grid or where the maximum allowed power is limited.
The situation described above applies to the Netherlands. As you can see, there are already quite a number of regions where there is a problem with the available capacity on the electricity grid.
When choosing between an ASHP and a GSHP, this is an important aspect to consider. At critical times, as already discussed above, a GSHP is more efficient than an ASHP, reducing the peak demand on the electricity grid and allowing for more connections. As a society, if we want to move towards renewable heating and cooling, opting for a GSHP is more beneficial than an ASHP, when grid infrastructure investments are taken into account.
Conclusion
Ground source heat pumps typically do not have the lowest investment costs, but probably their operational costs are lower. But besides economic reasons, there are quite a lot of reasons to opt for the geothermal solution from an individual/owner standpoint, as well as from a societal viewpoint. But one aspect remains crucial, and that is the design of the system. Let us take a closer look on why design matters and how we can do it, in our next chapter.
References
- Meggers, Forrest & Mast, Matthias & Leibundgut, Hansjürg. (2010). The missing link for low exergy buildings: low temperature-lift, ultra-high COP heat pumps.
- https://monarch.nl/wp-content/uploads/2025/10/Brochure-Geoblock-WGB-20-83602907.pdf [last visited 21/01/2026]