U.S. utility-scale solar installations – including both photovoltaic (PV) and thermal technologies – grew at an average rate of 72% per year between 2010 and 2016, faster than any other generating technologies, according to a new analysis from the U.S. Energy Information Administration (EIA).
The EIA says utility-scale solar generation now makes up about 2% of all utility-scale electric generation in the country. The first utility-scale solar plants were installed in the mid-1980s, but notably, more than half of the currently operating utility-scale solar capacity came online in the past two years.
As of December 2016, more than 21.5 GW of utility-scale solar generating capacity was in operation across the U.S., with more than 7.6 GW of that capacity coming online in 2016, according to the agency. Although California has the highest total installed capacity of any state, a number of states have deployed significant utility-scale solar capacity in recent years. The EIA notes several states have policies such as renewable portfolio standards or state renewable tax credits to encourage solar deployment, and since 2005, the federal government has provided a 30% investment tax credit, which is scheduled to phase down or expire by 2022.
Utility-scale solar generation has been increasing as a result of the rapid growth in capacity; however, the EIA says solar’s share of utility-scale electricity generation is 0.9%, about half of its share of capacity. Most solar generators are considered an intermittent or non-dispatchable resource because their availability depends on ambient insolation (exposure to the sun). The agency points out that some systems, such as the Crescent Dunes solar thermal plant, are paired with an energy storage system, which allows greater operational flexibility. As monthly capacity factors indicate, the EIA says solar generation is strongly seasonal, with more sunlight available in the summer (about 30% capacity factor, on average) than in the winter months (near 15%).
In addition to utility-scale solar, electric generating capacity from small-scale solar systems (such as rooftop and other customer-sited PV systems) has also grown. In 2016, the EIA estimates that the U.S. added 3.4 GW of small-scale solar generating capacity across all three end-use sectors (residential, commercial and industrial), ending the year with more than 13.1 GW of installed capacity. (EIA reports capacity values in alternating current output.)
According to EIA estimates, California, New Jersey, and Massachusetts had the most small-scale solar capacity with 5.4 GW, 1.3 GW, and 1.0 GW, respectively. Monthly generation from small-scale solar capacity is estimated to have been 1.6 million MWh on average in 2016, or about two-thirds of the amount generated by utility-scale solar generators.