Vertical vs. horizontal geothermal systems in Spain: permits, costs, and when to choose each

Geothermal energy is becoming one of the most efficient solutions for heating and cooling homes and buildings in Spain. However, one of the key steps before installing a geothermal heat pump is deciding between a vertical and a horizontal system, as each has different technical, regulatory, and financial requirements.

In this comprehensive guide, we examine the permits and updated costs for 2025, and provide a clear checklist to help you choose the best option for your project.

1. Horizontal geothermal systems: conditions and requirements

A horizontal ground loop involves burying pipes 1.2–2 m deep in a serpentine or spiral pattern, covering a plot area twice the size of the space to be heated and cooled.

• Land required: at least 400–600 m² of open land for an average detached house.
• Soil conditions: the wetter and more clay-rich the soil, the better its thermal conductivity.
• Restrictions: do not plant deep-rooted trees or cover the trench area with concrete.
• 2025 cost: between €8,000–€12,000 for a standard home (Ecoforest).
• Advantage: more affordable to install if sufficient space is available.
• Disadvantage: slightly lower performance, affected by seasonal variations in ground temperature.

2. Vertical geothermal systems: deep drilling

A vertical ground loop uses boreholes 50–150 m deep, with geothermal probes surrounded by bentonite and cement to ensure thermal contact.

• Requirements: at least 10 m² per borehole to allow drilling.
• Performance: more stable (30–70 W/m, depending on the ground’s thermal conductivity).
• 2025 cost: between €15,000–€25,000 for an average detached house (Ecoforest).
• Installation time: 5–7 days of drilling, 3–4 weeks in total for residential projects (Ecoforest).
• Advantage: takes up little space and works on small urban plots.
• Disadvantage: higher initial investment and drilling permits are required.

3. Permits and regulations in Spain (2025)

The procedures depend on the type of system:

• Horizontal: a minor works permit is usually sufficient.
• Vertical: requires a geotechnical report and notification of the drilling to the regional mining/energy authority. In practice, any borehole deeper than 30 m must be officially registered (Law 22/1973), and a minimum distance from foundations and trees (≥1.5–2 m) may be required (Ecoforest).
• Subsidies: IDAE and regional programs offer grants of up to €4,000 (horizontal) and €7,000 (vertical).

4. CAPEX and OPEX costs in 2025

A detached house in Bilbao with an €18,000 vertical system and annual savings of €1,200 → ROI ≈ 12 years (Ecoforest).

5. Decision checklist: vertical or horizontal?

• ✅ Choose a horizontal geothermal system if…
  • Your plot is large (>500 m² of open land).
  • You prefer a lower upfront cost.
  • You do not mind restrictions on how you use the land (such as not planting deep-rooted trees).
• ✅ Choose a vertical geothermal system if…
  • You have limited space or the home is in an urban area.
  • You want maximum seasonal performance that remains stable year-round.
  • You are looking for a longer service life (probes >50 years).

6. Conclusion

The choice between vertical and horizontal geothermal systems in Spain in 2025 comes down to three factors: available space, upfront budget, and the plot’s regulatory requirements. Both options can deliver savings of 60–75% on heating and cooling, but vertical systems offer higher, more stable performance without the land constraints of horizontal systems.

To learn more about the technology, we recommend reading our cornerstone article: Geothermal heat pumps: an efficient and environmentally responsible alternative. And if you would like to see real-world examples, visit our Ecoforest geothermal projects section, where we showcase both vertical and horizontal installations.