Geothermal or Air-to-Water Heat Pump? Big Comparison 2025

Choosing the right heating system is one of the biggest and most far-reaching decisions when building a detached house. The choice will not only affect future housing costs for decades, but also the comfort of living and the value of the property. Two of the most popular options for modern builders are geothermal and water-to-air heat pumps (VILP).

Both offer significant savings over traditional heating systems, but there are fundamental differences between them in terms of investment, efficiency and suitability. This comparison breaks down both systems and provides a fact-based basis for making a choice.

Differences in operating principles

Before comparing, it is important to understand the fundamental operating principles of the systems:

• Geothermal: Collects solar energy stored in the soil, rock or water. The energy collection pipeline is lowered into an energy well drilled deep into the ground or dug into the surface soil. The temperature of the ground is evenly cool all year round, which ensures a stable and high efficiency.
• Air-to-water heat pump (ATP): Collects energy from the outside air using a unit installed outside the house. This energy is transferred to the house's water-based heating system, such as underfloor heating.

Direct comparison: Five key points

1. Investment costs

The initial investment is often a significant factor in decision-making.

• Water-to-air heat pump: This is a significantly cheaper initial investment. The total price of the system when installed is typically 10,000–15,000 euros. The cost consists of the equipment and installation work.
• Geothermal: Requires a significantly higher initial investment, mainly due to the expensive drilling of an energy well or excavation of a ground circuit. The total price when installed is usually 20,000–30,000 euros.

Conclusion: A water-to-air heat pump is a more affordable initial investment.

2. Efficiency and SCOP value

SCOP (Seasonal Coefficient of Performance) tells you how efficiently a unit produces heat over the entire heating season. A higher number is better.

• Geothermal: Operates with very stable and high efficiency, as the temperature of the ground remains constant even in the coldest temperatures. A geothermal heat pump typically has a SCOP value of 4.5–5.5.
• Water-to-air heat pump: The efficiency is good, but it depends on the outdoor temperature. When the frost gets worse, the efficiency drops, and the device has to rely more on the electric resistance. The SCOP value of modern VILP systems is 3.5–4.5.

Conclusion: Geothermal energy is more efficient and stable.

3. Operating costs and payback period

• Geothermal: Due to its higher and more stable efficiency, geothermal energy produces the largest annual savings in heating costs. Although the initial investment is large, it pays for itself faster than a VILP system through greater savings, typically in 7–12 years.
• Water-to-air heat pump: Saves significantly compared to direct electric heating, but operating costs are higher than geothermal, especially in cold winters.

Conclusion: Geothermal energy offers better savings in the long term.

4. Site requirements and installation

• Water-to-air heat pump: Very flexible. It only requires space for the outdoor unit on the wall of the house, making it ideal for small plots and urban areas.
• Geothermal: Always requires drilling or extensive excavation. Drilling an energy well requires heavy equipment to access the site. Installing a geothermal circuit requires hundreds of square meters of free, excavable land.

Conclusion: A water-to-air heat pump is easier and more flexible to install.

5. Service life, maintenance and aesthetics

• Geothermal energy: The system is almost completely invisible and silent. The heat pump is protected indoors, and the energy well is underground. The well has a lifespan of over 50 years, and the pump itself is about 20–25 years.
• Water-to-air heat pump: The outdoor unit, installed outside the house, is visible and makes noise when operating. It is also exposed to weather conditions, which can shorten its lifespan (typically 15-20 years).

Conclusion: Geothermal energy is more sustainable and less noticeable.

• A water-to-air heat pump (VILP) is cheaper to purchase, but its operating costs are higher and its efficiency decreases in freezing temperatures.
• Geothermal energy is a more expensive initial investment, but it is the most efficient, most stable, and produces the greatest savings in the long term.
• The choice depends on the size of the plot, budget and personal priorities.
• Geothermal always requires drilling or excavation, VILP only requires space for the outdoor unit.
• Geothermal energy is practically silent and invisible, while the VILP outdoor unit is visible and produces sound.