California ranked as the state with the most aggressive energy-efficiency policies in an annual scorecard released this week by the nonprofit American Council for an Energy-Efficient Economy.

The report evaluated state efficiency policies in six areas, from utility programs to building codes and appliance standards. California has topped the group's national rankings in the three years the report has been produced. This year, the next-best states were Massachusetts, Connecticut, Oregon and New York. The five states doing the least to boost energy efficiency, according to the study, were Nebraska, Alabama, Mississippi, North Dakota and Wyoming.

Per-capita electricity consumption in California has been roughly flat over the last three decades, while it has risen about 40 percent in the rest of the country.

A 2008 Stanford University study found that state regulations account for 23 percent of the difference between California and the rest of the country. The balance, the study found, is likely due to factors like urbanization, loss of industry and shifts in the average number of people in a household.