File this one under Green.

Sometime in the near future, district heating in Helsinki will be supplemented by heat thrown off by local data centers. This will enable them to cut back on greenhouse gases produced by more traditional methods to heat the water that is pumping through radiators across town.

In a first of its kind experiment, the city of Helsinki will look at piping the waste heat produced by a data center, specifically the underground Academica Data Centre, to run under buildings and provide much needed heat for the residents. In a further move to enhance the greenness of this data centre, it is also going to be cooled by the icy waters of the Baltic Sea. This is one of the unique features of this system – the pump can both heat and cool water. This efficacy means that the output energy is five times more than the input energy. This directly translates into five times cheaper power. . . They can heat around 500 houses [and also save] around $ 563,000 annually for the company in power bills.

The Data Center Journal

Pretty nifty.