A few years ago someone introduced me to the collection of energy flow diagrams published by the Lawrence Livermore National Laboratory and the Department of Energy, under whose auspices the work was performed. The most recent diagram including the data for 2011 is included below, or at https://flowcharts.llnl.gov/.
There are a number of things that are interesting about the diagrams. First is the fact that from year to year to can see the rise or fall in overall energy consumption. For example, there was a huge decrease between 2008 and 2009; roughly 5% overall. This isn't surprising given the economic downturn and the number of business that either downsized or closed their doors and the general fact that many consumers tightened their belts as well. However, there was also a slight decrease (about 1/2%) between 2010 adn 2011. Because economists tell us that the recession ended prior to January 1, 2011, you'd think that the belt-tightening had ended and that these gains were due to improvements in energy efficiency. The 2012 data will allow us to see if this trend continues.
The second interesting observation is that on the output side of the flow diagram, more energy ends up in the "Rejected Energy" bucket than in the "Energy Services" bucket. This is the case for each of the diagrams on the front page of the Livermore site — going back through 2008. The footnotes explain the gymnastics the Livermore staff used to arrive at their conclusions but if their forumlas are correct, the diagram shows that there is a lot of room for improvement in the "Electricity Generation" sector of the economy. In fact, the rejected energy from electricity, 26.6 quadrillion BTUs is almost 1-1/2 times greater than the inputs from coal at 18.0 quadrillion BTUs. That makes prospect of effeciency improvements not only the "best fuel" for the economy, but also the greenest.