Gannett: In the absence of a national policy that puts a cap on carbon emissions, some environmental activists see an opportunity to place more emphasis on efficiency as part of the solution to climate change. Advocates say the potential benefits to the environment, the economy and individual pocketbooks cannot be ignored. One 2007 study estimates the U.S. could reap $1.2 trillion in electricity savings by investing $520 billion in energy-efficiency measures by 2020. “Energy efficiency …