States don't move towards cleaner forms of energy by accident. The ones with the most solar and wind, electric vehicles, and the like, have favorable conditions for those things to happen, chiefly available capital and technology, and enabling legislation and regulation.
That California "sets the pace for what a clean-energy economy looks like," in the words of research group Clean Edge, is a function of its ability to lay building blocks for its success.
California leads Clean Edge's U.S. Clean Tech Leadership Index, a ranking based on 70 indicators, by a wide margin. Out of a possible 100 points, the Golden State gets 94, with Massachusetts, in second place, on 79 points. California also leads on "deployments" of low-carbon electricity, clean transport, and energy-efficient buildings. It's also home to three of the top highest-ranking cities in a separate metro ranking: San Francisco, San Jose, and San Diego.
The biggest producers of clean electricity are not necessarily those states that come highest in the ranking overall. Idaho (83%), Washington (76%), Oregon (73%) and South Dakota (73%) have the highest percentages, if you include wind, solar, geothermal, hydro and biomass. Iowa and South Dakota produce the most wind energy (more than 25% of their total generation).
Clean Edge says Massachusetts has the best policies to encourage "cleantech," with 16 regulations and mandates, and 15 incentives. The top-10 for "policy" also includes Minnesota, New Mexico, and Illinois. North Dakota is last.
As for capital—which includes both the financial and human kind—that's the area where California's lead is strongest. In 2014, its total venture capital investments were more than four times its nearest competitor (Texas), while it also saw almost double the clean energy patents granted as second-placed Michigan.
See the full results, including all the metro rankings, here.