I wasn't expecting to see a Chicago publication touting Austin as a green energy capital, but here it is:

In 2001, [Chicago's Mayor] Daley promised to transition a fifth of the city’s electricity to renewable resources by the end of 2006, making him a favorite of environmentalists and eco-conscious celebs. However, with December fast approaching, Chicago is chugging along almost entirely from nuclear and coal fuel, leaving Austin and San Diego to take the honors as top buyers of green energy.

Austin and San Diego Kicking Our Green-Energy Ass, Chicagoist, November 27, 2006

I don't see any quantification on why Austin and San Diego in particular, but, hey, who am I to argue?

-jsq