U.S. Energy Use Dropped Over 2% in 2008; 57.5% of Energy "Rejected"

Americans used 99.2 quadrillion BTUs (known as “quads”) of energy in 2008, according to a report from the Lawrence Livermore National Laboratory. In 2007, we used 101.5 quads, which means our 2008 use fell by about 2.3%.

(A BTU or British Thermal Unit is a unit of measurement of energy, and is the amount of heat required to raise the temperature of one pound of water by one Fahrenheit degree. Click here for a longer definition.)

We consumed more energy derived from natural gas and renewable sources in 2008 than in 2007, while use of energy from coal and petroleum fell. Energy used for industrial and transportation purposes fell, which the Laboratory attributes to the rise in oil prices in 2008. Both these sectors depend heavily on petroleum.

Did that "rejected energy" mentioned in the headline pique your curiosity? A.J. Simon, an energy systems analyst at the Laboratory, explains the concept below. Simon creates the annual flowchart that shows the amount of energy generated by various sources and its distribution to different sectors.

Energy services, he says, refers to "the energy that makes your car move and that comes out of your light bulb.” That's "good" energy.

The remainder is rejected energy. “For example, some rejected energy shows up as waste heat from power plants,” Simon says.

The ratio of energy services to total energy is the country's energy efficiency. Ours stands at 42.48%. Put another way, we reject more than 57.5% of the energy we use.

Another reason to improve our collective energy efficiency.

Update on 7/30/2009:
Anne Stark, Public Information Officer at the Lawrence Livermore National Laboratory, provided a flowchart summarizing the 2007 estimated energy use in the U.S. It shows that last year, we rejected 58.47 quads or 57.6% of the energy used.

Which tells us that the nation's energy-efficiency improvement from 2007 to 2008 was less than 0.1 percentage point.

It's small, but we'll take what we can get.