October 17 marks the 40th anniversary of the start of the 1973 Arab Oil Embargo — an event that arguably launched the United States' ongoing pursuit of a national energy policy.
Forty years ago, the U.S. economy was dominated by fossil fuels (i.e., oil, coal, natural gas) which accounted for 93 percent of the nation's energy consumption. Petroleum — more than 30 percent of which was imported — accounted for almost half of fossil fuel consumption with roughly half used in the transportation sector and 17 percent burned to generate electricity.
In 1973, conventional hydropower generated almost 15 percent of the nation's electricity and provided 3.8 percent of its total energy consumption. Biomass claimed a 2 percent share of the nation's energy use but, like geothermal, provided less than 1/10th of a percent of the country's electrical generation. Energy produced by solar, wind, and biofuels was essentially non-existent.
The 42 nuclear reactors operating in 1973 provided 4.5 percent of U.S. electrical generation and satisfied just over 1 percent of the nation's total energy demand.
Four decades later, U.S. energy use in some areas appears to have changed only modestly. Fossil fuels, for example, still dominate and, in 2013, will account for roughly 82 percent of total energy consumption.
However, other energy technologies have experienced significant growth.
Nuclear power has increased nine-fold and now provides over 19 percent of U.S. electrical generation — roughly 8.2 percent of total U.S. energy use.
The mix of renewable energy technologies (i.e., biofuels, biomass, geothermal, hydropower, solar, wind) now accounts for 10 percent of energy consumption, 12 percent of domestic energy production, and 14 percent of net electrical generation.
Perhaps most significantly, major gains in energy efficiency mean that the energy intensity of the American economy today — measured as energy use per unit of GDP — is less than half of what it was forty years ago.
Energy Efficiency: Over the past four decades, U.S. energy use has increased by 28 percent from 75.6 quads in 1973 to about 97 quads in 2013. However, during that same period the nation's population has grown by 50 percent (from ~210 million in 1973 to ~315 million in 2013) and the nation's GDP (constant prices) grew from less than $6 trillion in 1973 to about $16 trillion in 2013.
Thus energy intensity, measured as energy used (thousand Btu)/real dollar of GDP (2009 chained dollar), dropped by more than half from 13.97 in 1973 to 6.15 in 2012 due to a combination of energy efficiency legislation, agency regulations, price signals, technological advances, and changes in consuming habits.
Had energy growth continued at the rates experience after World War II until 1973, energy use in the U.S. today would be at least 40 percent higher than it actually is making energy efficiency, in effect, the nation's largest "energy resource."
Yet, study-after-study suggests that the United States has still not picked all of the low-hanging fruit, much less implemented the more complex structural changes that could secure far greater gains in energy efficiency. Some analysts argue that energy intensity of the U.S. economy could be further reduced in the near term by 30 percent or more using cost-effective, currently-available technologies.
For example, after more than two decades of politically-based stagnation, gains are now finally being realized in auto fuel efficiency that could ultimately lead to a doubling of mpg, especially as hybrid, all-electric, fuel-cell and other alternative vehicles expand their market share.
A complete shift in the lighting market to compact fluorescents and LEDs could theoretically cut energy use in that sector by 75 percent or more. New buildings can be economically constructed that use 30 percent less energy (some would argue 50 percent or more) while existing buildings can often be upgraded to achieve gains almost as large.
Far greater use of cogeneration and waste heat recovery as well as smart grid and new transmission line technologies could greatly reduce energy losses in electrical generation, which typically wastes nearly two-thirds of the fuel consumed.
Renewable Energy: In 1973, renewable energy sources (i.e., biofuels, biomass, geothermal, hydropower, solar, wind) accounted for 6.9 percent of domestic energy production comprised of hydropower (65 percent) and biomass (35 percent) with a trace contribution from geothermal. There was essentially no contribution from biofuels, solar, or wind. In the electricity sector, hydropower accounted for 99.2 percent of all power generated by renewable sources.
By 2013, renewables accounted for almost 12 percent of domestic energy production with a mix of hydropower (29.7 percent), biomass (25.4 percent), biofuels (20.0 percent), wind (19.3 percent), solar (3.2 percent), and geothermal (2.4 percent). By mid-2013, renewables accounted for 14.2 percent of U.S. net electrical generation, with almost half coming from non-hydro renewables.
Renewables have now emerged as a major contributor to the nation's overall energy supply. Yet, it can be argued they are still well short of their real potential. For example, in 1980, a lengthy, inter-agency analysis conducted by the Carter Administration concluded that renewables could meet 20 percent of the nation's energy needs by the year 2000 (and some members of the task force argued a goal of 25 percent was doable). Yet, 33 years later, renewables have only reached the half-way point of the 2000 goal.