Why are Californians so much better at conserving energy than the rest of the country? At least, it looks like they are: Since 1975, per capita electricity use in California has barely budged, while it's shot up 50 percent across the rest of the United States. Some observers have credited the state's aggressive energy-efficiency policies—everything from installing LED traffic lights to painting roofs white to ensuring that residential air ducts don't leak heat. Meanwhile, California's "decoupling" laws have given electric utilities incentives to push energy-saving measures (in most states, utilities only make a profit if they sell, sell, sell).

These are all beguiling ideas, and the California Energy Commission claims that the state has achieved most of its energy savings—equal to about 15 percent of its annual electricity use—due to utility-led programs and strict appliance and building standards. But not everyone thinks things are quite so simple. Via Kate Galbraith, a new study by Cynthia Mitchell and two other co-workers at the consulting group Energy Economics Inc. argues that other, structural factors might explain more of California's success.

For one, California has higher electricity prices than the rest of the country, which helps drive consumption down. The state also has a milder climate than most other places (less air-conditioning), not to mention more multi-family urban households. And California has fewer energy-intensive industries: Manufacturing composes just 20 percent of the state's employment, compared with 26 percent nationally. Aluminum, a particularly energy-intensive sector, has seen a 40 percent employment decline in California since 1975, compared with 31 percent for the rest of the country. By contrast, California's pharmaceuticals sector doesn't pollute quite as much, and its computer and electronics manufacturers have been especially successful at reducing their energy intensity. (Though the latter might be a result of smart policies—that's unclear.)

So it's a muddled picture, and not every state could necessarily adopt California's policies and expect to see the same results (though surely they'd see some cuts). Still, it'd be foolish to write off efficiency policies entirely. They do have an effect: One recent study by Anant Sudarshan and James Sweeney of Stanfordtried to disentangle all the different structural factors and concluded that efficiency policies accounted for 23 percent of the gap in energy use between California and the rest of the country—nothing to sniff at. (Although, Mitchell points out, California's population is still growing, so even flat per-capita use won't curb emissions, which is what the state's new global-warming bill aims for.)

One interesting point Mitchell explores is which efficiency policies do best at driving down electricity use. Since the mid-1980s, building and appliance standards have been doing most of the work, while utility programs seem to have reached a saturation point with one-off savings early on. On the other hand, the report suggests that utility programs may have helped foster a "conservation ethic" in the state. One survey found that 60 percent of California households remember to turn down the thermostat when no one's home, compared with just 45 percent nationally. That's not a huge deal by itself, but it does suggest a different mindset might be at work, which can certainly make a difference.

(Flickr photo credit: sowellman)

--Bradford Plumer