Flow chart of 2011 US energy use

A flow chart released by the Lawrence Livermore National Laboratory illustrates the sources and uses of energy in the United States.  It depicts information about all the energy sources used to power society, as well as the breakdown of how that energy is used - or wasted - in electricity generation, transportation, residential, commercial, and industrial contexts.

On the energy source side, petroleum - oil, gasoline, and similar products - provides the largest share of the energy we consume, slightly more than a third of total energy.  Natural gas comes in second, providing about a quarter of total energy, with coal coming in at another 20%.  Altogether, these fossil fuels provided about 82% of the energy consumed in the U.S. in 2011.  Nuclear power provided about 8% of the energy used.  The remainder came from renewable resources including biomass, hydropower, wind, geothermal, and solar.

About 40% of the energy from these sources was used to generate electricity.  The remainder was used directly for other purposes such as transportation, heating, and industrial processes.

On the use side, transportation consumed the largest share of energy, about 28%.  The industrial sector consumed another 24% of the energy.  Households consumed about 11%, and commercial businesses consumed about 9%.

This analysis of energy use leaves about 27% of the energy unaccounted for.  This energy was consumed in the generation of electricity, but was "rejected", meaning that it could not be captured for a useful purpose.  Waste heat being emitted from a generator is a classic example of this rejected energy.  End users from industry to residences also waste or reject energy; in fact, according to the chart, 57% of the total energy consumed in the U.S. in 2011 was rejected, while only 43% was put to a useful purpose.