Improving energy efficiency in our homes, businesses, schools, governments, and industries which consume more than 70 percent of the natural gas and electricity used in the countryis one of the most constructive, cost-effective ways to address the challenges of high energy prices, energy security and independence, air pollution, and global climate change. Despite these benefits and the success of energy efficiency programs in some regions of the country, energy efficiency remains critically under utilized in the nations energy portfolio. It is time to take advantage of more than two decades of experience with successful energy efficiency programs, broaden and expand these efforts, and capture the savings that energy efficiency offers. Program evaluation that is based on credible and transparent model methods is a key component of the solution.