I always wondered, but not enough to do calculations, that if instead of increasing one's electricity bill by $10, one could donate $15 (tax deductible) to an organization to run the computation themselves. Which is more efficient?
They have to be electron-juice too, and while it might be cheaper for them to buy it, they also have to pay for hardware on top of it.
Option A) You spend $10 on electricity and give them X MIPS.
Option B) You give them $15, they spend $5 on electricity, and then they have $10 to spend on hardware. I bet that they'd get far less than X MIPS!