What energy could be cleaner and more cost-effective than energy that is never used in the first place? Energy efficiency is often considered a resource in its own right—a “hidden fuel” that has the potential to cut costs, increase energy access, reduce air pollution, and improve energy security, among other benefits. And, as the International Energy Agency has noted, energy efficiency “is the one energy resource all countries possess in abundance.” Mexico is one country in the region with extensive experience in this area; in fact, its program to improve energy efficiency in public buildings dates back to the 1990s.