Recent growth rates and price drops do suggest, though, that the use of renewables could greatly accelerate in the near-term. Between 2003 and 2012, for example, energy produced from wind increased by a factor of 12, biofuels output grew more than five-fold, and solar generation quadrupled. Geothermal also expanded by more than 30 percent. Only hydropower and biomass (other than biofuels) remained essentially unchanged.
Photovoltaic (PV) cell costs today are 1 percent of what they were in 1973. Wind energy costs have declined by as much as 50 percent in just the past four years. Combined with recent developments in a number of energy storage technologies, wind and solar are now either at, or close to, "grid parity" with fossil fuels — and, in some instances, actually cheaper. Moreover, the first significant amounts of cellulosic biofuels have been produced in just the past two years with production levels expected to ramp up significantly in the near term.
Nuclear Power: In 1973, the U.S. had 42 operating nuclear reactors that generated 4.5 percent of the nation's electricity. In response to the oil embargo, then-President Nixon called for the construction of 1,000 nuclear reactors. The resulting expansion in the 1970s came to a screeching halt with the 1979 Three Mile Island nuclear accident and subsequently resumed at a far-slower pace. By 2010, nuclear power had peaked when 104 reactors provided 11.3 percent of domestic energy production and 19.6 percent of the nation's electricity.
Nuclear generation has dropped each year since then and is likely to see further declines - at least for the next several years - in light of the recently announced closures of five reactors (Crystal River, Kewaunee, San Onofre-2, San Onofre-3, and Vermont Yankee). While five new reactors are now under construction, their eventual contribution to the nation's electricity supply (assuming they are ever completed) may well be off-set by retirements of other older, uneconomic, and arguably troubled reactors (e.g., Oyster Creek, Pilgrim, Indian Point, Fitzpatrick, Davis-Besse).
Petroleum: The total amount of oil used in 1973 (34.8 quads) has changed little over the past four decades (34.7 quads used in 2012) but its share of the nation's energy mix has declined from 46 percent to 36 percent. Notably, oil use for electrical generation has changed from 17 percent in 1973 to less than 1 percent in 2013. Roughly half the oil used in 1973 was for transportation; it is over 70 percent today.
Net oil imports (imports minus exports) rose from roughly 30 percent in 1973 to a high of over 60 percent in 2005 and have since been declining; the U.S. relied on net imports for about 40 percent of the petroleum (crude oil and petroleum products) that was consumed in 2012. Contributing to this decline has been:
Natural Gas: Domestic consumption of natural gas has increased by 26 percent over the past four decades but remained at about 29 percent of the total energy mix. Its use in the electricity-generating sector has tripled since 1973 and its share of net electrical generation has increased from 18.3 percent in 1973 to 26.2 percent in 2013. (By comparison, electrical generation more than doubled between 1973 and 2013.)
Coal: Domestic production of coal has increased by over 40 percent over the past four decades (13.99 quads in 1973 to 19.79 quads in 2013) but its share of the nation's overall energy consumption has remained relatively unchanged (17.1 percent in 1973 vs. 17.6 percent in 2012). Further, its role in electrical generation has dipped in recent years from about 45 percent in 1973 to about 39 percent in 2013, reflecting increased competition from both natural gas and renewables.
CO2 Emissions: Carbon dioxide (CO2) emissions from energy consumption today are about 15 percent higher than they were 1973. The 2013 figure actually represents a drop of 11 percent from the peak level recorded in 2007 with the decline attributable to the economic recession, some displacement of coal by natural gas, increased use of renewables, and improving energy efficiency.
The recent downward trend, however, is almost certainly not large enough or fast enough to counter global increases in CO2 emissions or to substantially reduce the risks posed by climate change.
Coal accounted for about 25 percent of CO2 emissions from energy consumption in 1973 but its share had risen to almost 30 percent by 2012 with actual CO2 emissions from coal rising 37.3 percent over the past four decades. By comparison, petroleum was responsible for ~40 percent of CO2 emissions in 2012, natural gas for ~24 percent, and biofuels/biomass for ~5 percent.
Lead image: Embargo via Shutterstock