Glenn McGrath / Principal Contributor / U.S. Energy Information Administration (EIA) Analyst
U.S. solar capacity increased significantly in the last 4 years. In 2010, the total solar capacity was 2,326 MW, which accounted for a comparatively small fraction (0.22%) of the total U.S. electric generating capacity. By February 2014, this capacity increased 418% to 12,057 MW, a 9,731 MW gain, and now accounts for almost 1.13% of total U.S. capacity. Reported planned solar capacity additions indicate continued growth.
EIA tracks three principal types of solar-electric generating capacity:
1. Residential and commercial rooftop and other PV capacity reported by distribution utilities as net-metered.
2. Utility level (>= 1 MW) solar photovoltaic capacity reported by generation operators.
3. Utility level (>= 1 MW) solar thermal capacity reported by generation operators.
Net-metered applications, which are generally intended to displace retail purchased power to lower the overall energy bill for a host site, have increased each year since 2010 at an annual rate of about 1,100 MW and now total 5,251 MW. Although sunny California has the largest net-metered solar capacity (38% of the total), abundant sunshine is not the only growth factor for this sector. Net-metered applications are typically incentivized through various state level programs. New Jersey and Massachusetts together represent an additional 21% of the total net-metered solar capacity. Overall, the national growth in net-metered PV capacity is fairly evenly split between residential and commercial applications.
Photo courtesy of U.S. Energy Information Administration
Utility scale PV applications, which are 1 MW or greater, have also expanded significantly and currently account for 5,564 MW. In 2013 utility scale solar exceeded the capacity of net-metered applications. Utility scale PV applications generally provide wholesale electric power (although there are exceptions in the 1-3 MW range where some utility scale applications are net-metered).
The growth in utility scale PV applications is driven by many of the same factors behind net-metered applications. Sunny states like California (2,702 MW, 49% of the total utility scale PV) and Arizona (960 MW, 17%) enjoy favorable siting conditions. However, North Carolina accounts for 340 MW, or 6%, of the total utility level solar capacity, and is the third leading state in this sector largely due to state incentives. While North Carolina has a modest net metered solar capacity, just 11.6 MW, or 0.2%, of the total net-metered capacity, its large utility scale PV total indicates a diverse approach among state strategies to increase the level of renewable participation.
The third principal contributor to the large increase in solar capacity comes from thermal applications. These are distinct from PV applications in that solar energy is used to generate heat in a working fluid, which is then converted to mechanical energy in a turbine, then to electrical energy in a generator. Historically, the thermal solar application sector consisted primarily of a set of facilities near San Bernadino, California, SEGS I through SEGS IX, which account for 400 MW of capacity.
The thermal solar sector expanded significantly in 2013 when three large plants, Solano, Genesis, and Ivanpah, went online, adding a total of 650 MW of capacity. Solano is a particularly distinctive application in this sector due to its storage capability that extends the daily operating period and cushions sudden drops in output due to interruptions from passing clouds.
Each of the three sectors that have contributed to the significant overall solar gains, also has strong near term growth prospects. Currently, there are 6,459 MW of proposed utility scale PV and 1,841 MW of proposed thermal solar. Many of the same factors driving utility-level solar are expected to push net-metered capacity as well.
In summary, the U.S. solar capacity has moved quickly from a relatively small contributor to the nation’s total electric capacity into a one of comparative significance. Much like the wind sector growth, which grew tremendously from 6,456 MW in January 2005 to 60,661 MW to January 2014, solar capacity is quite clearly up and coming.