Austin is the leading cleantech city in the U.S.:

On a list of the nation's top five "cleantech" communities, Berkeley ranked third, according to a survey released Tuesday by SustainLane, a San Francisco-based online resource for sustainable living. The leading cleantech cities are developing solutions aimed at providing the world with biofuels, renewable energy and other clean technologies.

San Jose placed second on the list, thanks to projects that focus on solar energy and nanotechnology. The leading city was Austin, Texas, home to seven startups active in wind and geothermal energy technologies and other sectors.

The list was compiled by looking at cities that attract venture capital and networking activity, research universities and government support of clean technologies.

Berkeley in top five clean cities, By Eve Mitchell, ContraCostaTimes.com, MEDIANEWS STAFF, 28 February 2007

The quoted article managed to headline a California city nonetheless.

Here's the actual list of cities. It says:

SustainLane Government analyzed US cities to see which led in combining Cleantech investments, infrastructure and supportive policies into a physical “cluster.� The ideal existing model for a Cleantech incubation cluster combines:

• Start-up or advanced stage venture capital (VC) and investor network access, including mentoring.
• Academic or federal research lab collaboration.
• Active state or local government participation (field testing, prototyping, and pilot programs) and incentives.

That sounds like Austin's usual brand of city-county-state-academic collaboration on attracting the kind of industry it decides it wants.

-jsq