Energy efficiency is probably the cheapest, easiest renewable resource we have available to us. For a long time, energy was cheap and national policy was to make it as cheap as possible. That's left us with a legacy of infrastructure and appliances built on the assumption that wasteful use of energy is no big deal. But it is a bit deal and we have a lot of the needed technology and know-how needed to deal with it. Which I assume is what Barack Obama was getting at when he said this at an energy town hall meeting today:

Finally, one of the fastest, easiest, and cheapest ways to conserve energy and use less oil is to make America more energy efficient and more competitive with the world. That’s why, when I’m President, I will call on business, government, and the American people to make America 50 percent more energy efficient by 2030.

But what does it mean to become "50 percent more energy efficient"? Does that mean we'll use half as much energy? That our GDP's energy intensity will be cut in half? Or that there's some measure of "energy efficiency" such that 2030 energy efficiency will be fifty percent larger than in 2008? Unfortunately, efficiency is a difficult subject to talk about. An SUV could have an engine that's "more efficient" than the engine on a moped (i.e., it does a better job of converting a given quantity of gasoline into horsepower) while still getting many fewer miles per gallon. I was in an elevator earlier today where the lights were freakishly dim, and a woman in there with me speculated that it might be for energy efficiency purposes, but dimming the lights isn't really the same as making them more efficient.

Photo by Flickr user thingermajig used under a Creative Commons license