The area of Päijät-Häme is one of the best places in Finland for a novel type of heating system directly utilizing groundwater as a heat source for heat pumps. Groundwater heat pumps use groundwater as a heat source instead of the ground or air. Pumped directly into the pumps’ heat exchanger, groundwater is an excellent and mechanically simple heat source. Groundwater has the benefit of remaining at a nearly constant temperature regardless of the weather and time of the year, giving it a constant level of efficiency, which is not found in other ambient energy using heating systems. Utilizing groundwater allows for huge savings in energy consumption and emissions when it is used to replace electrical or oil-based heating. (Kouvo 2017)   

Groundwater heating is still very rare in Finland despite becoming increasingly popular in Sweden since the 1990s and even greater popularity in other nations such as the Netherlands. Only a handful of groundwater heating systems have been adopted in Finland, one of the first being Upontalo in Lahti which has since 2018 been almost entirely heated with groundwater heat pumps. (Tekniikka & Talous 2020).

Picture 1. Basic groundwater heating/cooling system. Water is pumped through the heat pump system and absorbed back down another well. (Arola & Huusko 2019)

A matter of geology 

Thanks to the geology of Salpausselkä ridge formation, the area around of Hollola-Lahti-Nastola is uniquely well suited for use of groundwater heating. Population centres have a warming effect on the groundwater around them and the bedrock of Salpausselkä has excellent heat transfer and storage capacity. These population centres being placed on such favourable ground has created unique potential in the region. This can be seen in Picture 2 taken by the Maankamara mapping tool made by the Geological Survey of Finland which shows the heating potential of aquifers around southern Päijät-Häme. 

As a part of research in an Interreg Europe funded RESINDUSTRY project, aimed at furthering the adoption of renewable energy in industry, we have presented the potential for groundwater heating use to the regional council of Päijät-Häme as part of the research for a regional Climate Action Roadmap. A more detailed article on this topic can be found in Finnish in LAB Pro journal titled Päijät-Hämeen alueen pohjavesienergiapotentiaali.  

Picture 2: Map of the area around Lahti from Geological Survey of Finland, showing the heat power potential of different aquifers. Green <100 kW, Blue <200 kW, Yellow <500 kW, Red >500 kW. (Geologian tutkimuskeskus 2018)



Paavo Lähteenaro works as energy issues expert in LAB University of Applied Sciences, working in the Interreg Europe funded RESINDUSTRY project with the aim of furthering the adopting of renewable energy sources in industry. 


Arola T. & Huusko A. 2019. Geologian tutkimuskeskus. Pohjavesienergian hyödyntämisen esiselvitykset Nastolassa – yhteenvetoraportti. [Cited 30.11.2020]. Available at:  

Geologian tutkimuskeskus. 2018. Maankamara. [Cited 28.11.2020]. Available at: &nbsp;