Last Thursday, Maryland Governor Martin O’Malley (D) signed into law the first statewide energy efficiency legislation in the nation. House Bill 374, the Empower Maryland Energy Efficiency Act of 2008, requires a 15 percent decrease in per capita energy use and peak demand energy demand by 2015.

To achieve these ambitious goals, Maryland’s public utility commission will more closely track energy use across the state and require energy providers to adopt energy efficiency measures. The law goes into effect this July, and electricity providers have to submit the first of mandatory planning and progress reports by September 1.

ClimateWire (subscription required) reported that the law stands to save Maryland ratepayers some $5.7 billion and avoid three new power plants. With about 5.6 million people, Maryland is the 19th-most populous state in the union, so it’s a good case for some basic extrapolations. If all 50 states and DC enacted energy efficiency legislation similar to Maryland, we’d save some $291 billion on energy costs and avoid more than 150 new power plants.

Forget all this talk of needing more energy, let’s make the most of what we’ve already got!