I'm becoming more involved in the analysis of oil and energy usage worldwide, and I found this little diagram just now that's rather helpful in understanding where US energy sources come from and whom they supply. (Click on the diagram to enlarge.)
Source: Energy Information Administration, Annual Energy Review 2006, Tables 1.3 and 2.1b-2.1f, and 10.3.
On the left side are the basic sources of energy: petroleum, natural gas, coal, renewable energy sources (such as solar power, ethanol, etc.), and nuclear energy. The right side shows, on a very basic level, who gets that energy: transportation, industrial, residential & commercial, and electric power. Now, obviously, industrial and residential & commercial, all get electricity, but the government has split that source of power out separately. Each of the sources and sectors have their own percentage, showing how much each contributes and consumes, respectively.
The lines connecting the two sides also have two sets of numbers each. For example, 100% of nuclear power obviously goes to electric power; however, nuclear power only makes up 21% of all the electrical power in the US. Likewise, transportation derives 96% of all its fuel from petroleum; natural gas and renewable energy sources (e.g., ethanol) only supply 2% each of transportation's fuel needs.
* Percentages do not necessarily equal 100% due to rounding.
1 Excludes 0.5 quadrillion Btu of ethanol, which is included in "Renewable Energy.”
2 Excludes supplemental gaseous fuels.
3 Includes 0.1 quadrillion Btu of coal coke net imports.
4 Conventional hydroelectric power, geothermal, solar/PV, wind, and biomass.
5 Includes industrial combined-heat-and-power (CHP) and industrial electricity-only plants.
6 Includes commercial combined-heat-and-power (CHP) and commercial electricity-only plants.
7 Electricity-only and combined-heat-and-power (CHP) plants whose primary business is to sell electricity, or electricity and heat, to the public.