When it comes to understanding how we produce and consume energy in the United States, one of our favorite resources is the Lawrence Livermore National Labs Energy Flow Charts. Here's the one for 2015 which, as of this post, is the most recent:
The way this flow diagram works is each source of energy is at the left, and as it flows towards the right, the thickness of the lines represent quantity, and the boxes the flows pass through show how that energy is used.
There are a few things to notice on this flow chart:
- The U.S. consumed 97.5 Quads of energy in 2015. One quad is a unit of energy equal to 1,000,000,000,000,000 BTUs, or the energy used by 33,433,418 hair dryers running continuously for one year.
- Roughly speaking, petroleum fuels cars and trucks while coal and renewable sources generate electricity for homes. Natural gas is used about equally for generating electricity and for generating heat in homes and industry.
- The pale gray box labeled "Rejected Energy" refers to energy lost as heat rather than doing the intended work. The majority of the energy we use in the United States ends up as wasted heat.
The great news is that LLNL has been generating these charts for decades. It's informative to look though their archives and see what has changed over time. For example, if you go back ten years, you will see the following:
- Between 2005 and 2015, the annual consumption of energy in the US decreased slightly from 100.4 quads to 97.5 quads.
- Contributors to that decrease include more efficient vehicles, decreasing to 27.7 quads from 28.3. The generation of electricity has also become more efficient: although slightly more electricity was consumed in 2015 than in 2005, the generation of that electricity required less source energy -- it fell to 38.0 quads from 39.71 quads.
- If you have been told that renewable energy is killing the coal industry, look again. It's true that coal energy usage fell to 15.7 from 22.79 quads over the last decade -- that's a big decline. But most of that decline is due to the increased use of natural gas for generating electricity: it increased to 9.99 from 6.01 quads over that time span.
One of the very thinnest lines on the 2015 chart is one of the most interesting: the line that shows the flow of electrical energy into the transportation sector. In 2015, it represented only only 0.03 Quads, but it will be interesting to track how that flow increases with increased adoption of Electric Vehicles.