http://www.geek.com/news/german-cloud-provider-will-heat-your-house-if-you-let-them-install-a-server-1609178/
"As for what counts as “expensive?” Cloud & Heat charges €12,000 up front for installation of the fireproof server cabinet. They cover all the other costs for a minimum of 15 years — broadband, electricity, maintenance. That works out to about €66 a month, which may not make it a sound investment for some… but it’s a pretty geeky way to heat your house."
Would you do this if the even though the cost is subsidized? I personally would if I had the cash upfront and was able to use a tray or two in the rack.