The National Academies have posted a nice visualization of the U.S. energy system, including where the energy comes from, how it is used, and how much is wasted. Bottomline: America consumed about 99 quadrillion BTUs (quads) in 2008. Of that, 42 quads were used by homes, businesses, factories, cars, trains, and planes. The remainder — 57 quads — was spent in generation, refining, transmission, distribution and efficiency losses. In other words, for every 100 BTUs we use, we waste another 135 BTUs. Ouch. Considering that energy is a $6 trillion global sector (and growing), figuring out how to reduce all this shrinkage sounds like a big business opportunity.