In addition, seven "units" of biomass (102 MW) and five units of solar (31 MW) came into service accounting for 12.16 percent and 3.69 percent of new capacity respectively. The balance came from three units of natural gas (132 MW - 15.73 percent).

Moreover, for the eighth time in the past ten months, renewable energy sources (i.e., biomass, geothermal, hydropower, solar, wind) accounted for the majority of new U.S. electrical generation brought into service. Natural gas took the lead in the other two months (April and August).

Of the 9,903 MW of new generating capacity from all sources installed since January 1, 2014, 34 units of wind accounted for 2,189 MW (22.10 percent), followed by 208 units of solar - 1,801 MW (18.19 percent), 45 units of biomass - 241 MW (2.43 percent), 7 units of hydropower - 141 MW (1.42 percent), and 5 units of geothermal - 32 MW (0.32 percent). In total, renewables have provided 44.47 percent of new U.S. electrical generating capacity thus far in 2014.

The balance came from 45 units of natural gas - 5,373 MW (54.26 percent), 1 unit of nuclear - 71 MW (0.72 percent), 15 units of oil - 47 MW (0.47 percent), and 6 units of "other" - 7 MW (0.07 percent). There has been no new coal capacity added thus far in 2014. Thus, new capacity from renewable sources in 2014 is more than 37 times that from oil, coal, and nuclear combined.  

Renewable energy sources now account for 16.39 percent of total installed operating generating capacity in the U.S.: water - 8.44 percent, wind - 5.39 percent, biomass - 1.38 percent, solar - 0.85 percent, and geothermal steam - 0.33 percent.  Renewable energy capacity is greater than that of nuclear (9.23 percent) and oil (3.97 percent) combined. Note that generating capacity is not the same as actual generation. Generation per MW of capacity (i.e., capacity factor) for renewables is often lower than that for fossil fuels and nuclear power. Actual net electrical generation from renewable energy sources now totals almost 14 percent of total U.S. electrical production according to the most recent data (i.e., as of August 2014) provided by the U.S. Energy Information Administration; however, this figure almost certainly understates renewables' actual contribution because EIA does not fully account for all electricity generated by distributed renewable energy sources.

Congress is debating whether to renew the production tax credit for wind and other renewable energy sources. The continued rapid growth of these technologies confirms that the PTC has proven to be a very sound investment.

Lead image: Wind turbine via Shutterstock