ESi ground source heat pump

Flexible geothermal energy solution

Even for demanding heating needs


Part of the Oilon and Lämpöässä ground source heat pump range, ESi is a flexible solution that has been awarded the best A+++ energy classification and the EHPA QL quality label. ESi heat pumps are typically used for heating in single-family homes, terraced houses, industrial locations, and farms. The heat pump’s ÄssäControl system even allows the system to utilize waste heat from different active cooling and refrigeration solutions used in agriculture and other fields. The heat pumps in the ESi range are especially suited for locations with limited installation space available or where an existing heating system will be used with the heat pump or as a backup system.

ESi heat pumps connect to an external storage tank. This makes them a good fit for locations with exceptionally heavy domestic hot water usage. If more capacity is required, you can connect several ESi heat pumps in parallel. An ESi heat pump works equally well in buildings with very low domestic hot water consumption as well as locations that already have a compatible, well-maintained single-section domestic hot water tank. ESi units can be connected to an ÄssäCooling system or to separate solar collectors.




  • An EHPA Quality Label product: The first range of heat pumps in Finland to receive the EHPA Quality Label (EHPA QL), a quality label provided by the European Heat Pump Association.
  • Safe choice: Long factory warranty combined with excellent Finnish craftsmanship.
  • Maximize your savings with unique technology: The heat pump uses only geothermal energy for space heating and domestic hot water production all year round.
  • Flexible and compact: ESi heat pumps are easy to transport, and they adapt flexibly to even the most demanding needs.
  • Control for three heating circuits: Split different areas (such as wet areas) into their own zones for temperature control, or control your domestic hot water circuit. Optional accessory.
  • Easy-to-use and clear control system: Developed in Finland, the ÄssäControl system provides a clear interface for controlling your home’s heating anywhere.
  • Extensive scope of delivery: Thanks to the extensive scope of delivery, there will be no unexpected extra costs and installation is quick and easy.


Applications: buildings up to 500 m²


Extensive control and management system


The ÄssäControl system used in ESi heat pumps has a clear touch screen with versatile function shortcuts, making it easy to control your heat pump. If required, you can even monitor and control your heat pump with a mobile device. Remote control for the geothermal heating system is provided as an option.

To read more about ÄssäControl, download our brochure:


Or watch the video:


The most economical cooling solution


All Oilon and Lämpöässä ground source heat pumps can be equipped with ÄssäCooling units, allowing you to cool your home during the summer months at a lower cost than any other system.


Unique technology


Fine-tuned over several decades, our superheat technology enables your heat pump to produce domestic hot water as a side product of heating, making your system exceptionally self-sufficient. Thanks to our advanced superheat technology, domestic hot water is heated up to the required level 100% with geothermal heat. Consequently, if you select the heat pump’s heating capacity based on the coldest winter day, the heat pump’s electric immersion heater will never be used in normal operation. Your heat pump will be able to provide space heating and produce domestic hot water at the same time, meaning that your home’s heating won’t be shut off even if you take a warm bath.

ESi can also be connected to your building’s system without the desuperheating circuit. This option is used when very little or no domestic hot water is used, or the building has an existing single-section storage tank that can be used with the heat pump. Even in this case, the heat pump will provide heating and produce domestic hot water with the same A+++ energy efficiency.



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Sales contact information

Aarnio Markus

Markus Aarnio

Sales Manager
p. 044 7576 411

Laaksonen Mikko

Mikko Laaksonen

Sales Manager
p. 044 7576 288

Petri Virta

Export Director,
Ground Source Heat Pumps
p. 044 7576 259