We’ve been having fun today calculating how to move jobs around in the day and night based on local temperatures. We heart playing with graphs.
For example, AWS Sao Paulo has a very green local energy grid so is generally a good choice, but it’s hot (27c daytime max this time of year), so the server cooling cancels out a lot of the environmental benefits. Oregon is looking pretty good so far, though: 9c daytime max in February and an okayish local grid, so even though it’s got a not-as-green power supply, it’s often a better choice than Brazil.
Just based on Amazon and Rackspace locations so far, I reckon you can save about 90% of potential emissions in winter and 95% in summer by picking the best location.
The time zone calculations are going to be a bit of a mare, though.