This text is from the Celsius Wiki, which was published between 2015 and 2018.


Figure 1. Source: Calefa

Figure 2. Source: Calefa

This case study is part of a project catalogue produced by ReUseHeat to provide inspiration on how to utilize excess heat from urban sources for heating and cooling purposes. The catalogue contains 25 existing or planned projects out of which 12 cases are Danish and 13 cases are from other European countries.


The city of Mäntsälä located approximately 55 km north of the Finish capital Helsinki, installed a heat pump capable of supplying 1500 homes with heating. The heat pump extracts heat from a nearby data centre.

Hot air from data centres holds a huge potential for energy recovery. By removing the air and utilizing the excess heat it can be used in local district heating networks. In 2015 Mäntsälä installed a 4.0 MW heat pump which utilizes the excess heat from the local Yandex data centre.

Heat exchangers extract hot air from the data centre servers at temperatures of approximately 40 degrees Celsius. This is used in the heat pump, where the temperature is increased to approximately 85 degrees Celsius. The heat pumps are optimized to achieve high temperatures hereby having a high COP, which potentially can be above 4.0. The heat pump does not affect the design of the data centre, as energy is harvested from the outgoing airstream. Extra fan-power is merely added to the building to extract the heat from servers.

By extracting waste heat from the computing centre, 75% of the energy originally used can be reused. Further, the excess heat replaces natural gas heating and hereby reduce the annual CO2-emission with approximately 4000 ton CO2 in the first years, which later can be up to 11,000 ton CO2. Currently the heat pump can supply 1500 homes with heating through the district heating network. Later, as the district heating network is to be expanded, this number can rise to about 4000 homes.

Facts about the case
Installed heat capacity:
4.0 MW
Heat source:
Cooling of data centre (40°C)
Heat pump COP:

11,000 ton CO2 annually
June to December 2014


Mäntsälä, Finland



Time plan

June to December 2014


External website

Send us an email

9 + 10 =

Share This
Toolbox Technical solutions Case studies technical solutions A datacentre supplies local heating in Mäntsälä, Finland