Most Sustainable/Renewable US Cities

As I gear up to travel around the US to research my book, I've been curious about which US cities are considered to be the most sustainable/green/into renewable energy.  So I did a quick search and founds dozens of "Top Ten" lists and the like (some are actually top 15 and longer).

A website called sustainlane lists the following cities as the "Top Ten US Cities for Renewable Energy":

1. Oakland, CA 2. Sacramento/SF/San Jose, CA 3. Portland, OR 4. Boston 5. San Diego 6. Austin, TX 7. Los Angeles 8. Minneapolis, MN 9. Seattle 10. Chicago

Smarter Cities, meanwhile, ranks the following 15 US large cities as the most sustainable:

1. Seattle, 2. SF, 3. Portland, 4. Oakland, 5. San Jose, 6. Austin, 7. Sacramento, 8. Boston, 9. Denver, 10. Chicago, 11. San Diego, 12. NYC, 13. LA, 14. Dallas, 15. Columbus, OH.

Not too many surprises, I suppose. I wasn't aware that Oakland, CA is such a mecca of sustainable living. And I might not have assumed that LA, NYC, Chicago, Dallas, and Columbus would be so high up on the lists. Given the things we usually associate with metropolisis like NYC and LA--traffic, dirt, smog, garbage, etc.--they just don't seem like they'd be so conducive to renewable energy and conservation and sustainability and so on. Although architect/urban planner/all-around smart guy Mitchell Joachim once did explain to me that NYC is in many ways a model of sustainable living, given its housing density, walkability, robuts public transport, and access to green spaces (Central Park, mostly).

I know these lists are largely subjective, and the criteria involved in ranking cities is open to critique. But it's stil interesting to look at lists like these. It raises interesting questions: what makes a city "sustainable"? How does urban planning factor into energy use and production? 

For some reason I wasn't able to easily find a list of the most sustainable cities worldwide.  If anybody finds a good list, let me know.