"Thus, we decided to only run computations when the outdoor temperature near the user is below a certain level (currently 16 degrees Celcius). When it's that cold outside, we assume that the computer's room is being heated anyway. All of the electricity used to do computations gets turned into heat, according to the laws of physics. So the heat generated by the computations displaces the need for heat generated by a heater, eliminating or minimizing the net elecricity usage."https://gridspot.com/gridspot_safe
Doesn't work in the USA. Natural gas heating in the US averages $10.80/thousand cubic feet ~= $10/gigajoule [1]. Electricity averages $0.1179/kWh ~= $33/gigajoule [1] -- more than three as expensive for raw heat. Natural gas heating is twice as common in US homes, with about 55.6 million vs. 28.4 million using electric resistance heating [2] -- not including 9.8 million electric heat pumps.
In the common case, you're displacing cheap gas heating with expensive electric resistance heating; the cost "savings" on heating is small. At 100W power consumption, you're spending 1.2 cents/hour on electricity, saving 0.4 cents/hour on gas, for a net loss of 0.8 cents/hour. Meanwhile your CPU is being sold for 0.1 - 0.3 cents/hour [3] -- far less than the electricity needed to run it, apparently (?).
[1] http://www.eia.gov/forecasts/steo/report/prices.cfm (residential retail prices, 2011)
[2] (.xls) http://www.eia.gov/consumption/residential/data/2009/xls/HC6...
[3] https://gridspot.com/compute/
European costs for comparison:
[4] http://www.energy.eu/