Solar power in the United States includes utility-scale solar power plants as well as local distributed generation, mostly from rooftop photovoltaics. As of the end of 2016, the U.S. had 40 gigawatts (GW) of installed photovoltaic capacity, having almost doubled in capacity from the previous year. In the twelve months through January 2017, utility scale solar power generated 35.5 terawatt-hours (TWh), 0.92% of total U.S. electricity. During the same time period total solar generation, including estimated distributed solar photovoltaic generation, was 57.2 TWh, 1.40 % of total U.S. electricity. In terms of total installed capacity, by year end 2015 the USA ranked 4th in the world behind China, Germany, and Japan. In 2016, 39% of all new electricity generation capacity in the country came from solar, more than any other source and ahead of natural gas (29%). By 2015, solar employment had overtaken oil and gas as well as coal employment in the U.S.
The United States conducted much early research in photovoltaics and concentrated solar power. The U.S. is among the top countries in the world in electricity generated by the Sun and several of the world's largest utility-scale installations are located in the desert Southwest. The oldest solar power plant in the world is the 354-megawatt (MW) SEGS thermal power plant, in California. The Ivanpah Solar Electric Generating System is a solar thermal power project in the California Mojave Desert, 40 miles (64 km) southwest of Las Vegas, with a gross capacity of 392 MW. The 280 MW Solana Generating Station is a solar power plant near Gila Bend, Arizona, about 70 miles (110 km) southwest of Phoenix, completed in 2013. When commissioned it was the largest parabolic trough plant in the world and the first U.S. solar plant with molten salt thermal energy storage.
There are plans to build many other large solar plants in the United States. Many states have set individual renewable energy goals with solar power being included in various proportions. Governor Jerry Brown has signed legislation requiring California's utilities to obtain 50 percent of their electricity from renewable energy sources by the end of 2030.
A 1997 report by the United States Department of Energy found available domestic solar energy (including biomass) technically accessible regardless of cost amounted to 586,687 Quadrillion BTUs (Quads); 95% of this was biomass. Coal represented the second largest resource, a distant 38,147 Quads. Predictions of how much solar power was economically feasible to collect amounted to 352 quads, compared with 5,266 quads from coal. The assumptions used in the report were based on a predicted 2010 price of a barrel of oil being $38, and multiplied annual renewable resources by 30 for comparison with non-renewable resources.The total annual energy consumption of the United States in 2007 was approximately 100 Quads, less than 0.5% of what is theoretically available from sunlight.
A 2012 report from the National Renewable Energy Laboratory described technically available renewable energy resources for each state and estimated that urban utility scale photovoltaics could supply 2,232 TWh/year, rural utility scale PV 280,613 TWh/year, rooftop PV 818 TWh/year, and CSP 116,146 TWh/year, for a total of almost 400,000 TWh/year, 100 times current consumption of 3,856 TWh in 2011. Onshore wind potential is estimated at 32,784 TWh/year, and offshore wind at 16,976 TWh/year. The total available from all renewable resources is estimated at 481,963 TWh/year.
Solar energy deployment increased at a record pace in the United States and throughout the world in 2008, according to industry reports. The Solar Energy Industries Association's "2008 U.S. Solar Industry Year in Review" found that U.S. solar energy capacity increased by 17% in 2007, reaching the total equivalent of 8,775 megawatts (MW). The SEIA report tallies all types of solar energy, and in 2007 the United States installed 342 MW of solar photovoltaic (PV) electric power, 139 thermal megawatts (MWth) of solar water heating, 762 MWth of pool heating, and 21 MWth of solar space heating and cooling.
A report finds that solar power's contribution could grow to 10% of the nation's power needs by 2025:
"The report, prepared by research and publishing firm Clean Edge and the nonprofit Co-op America, projects nearly 2% of the nation's electricity coming from concentrating solar power systems, while solar photovoltaic systems will provide more than 8% of the nation's electricity. Those figures correlate to nearly 50,000 megawatts of solar photovoltaic systems and more than 6,600 megawatts of concentrating solar power.
"As noted in the report, solar power has been expanding rapidly in the past eight years, growing at an average pace of 40% per year. The cost per kilowatt-hour of solar photovoltaic systems has also been dropping, while electricity generated from fossil fuels is becoming more expensive. As a result, the report projects that solar power will reach cost parity with conventional power sources in many U.S. markets by 2015. But to reach the 10% goal, solar photovoltaic companies will also need to streamline installations and make solar power a "plug-and-play" technology, that is, it must be simple and straightforward to buy the components of the system, connect them together, and connect the system to the power grid.
"The report also places some of the responsibility with electric utilities, which will need to take advantage of the benefits of solar power, incorporate it into future "smart grid" technologies, and create new business models for building solar power capacity. The report also calls for establishing long-term extensions of today's investment and production tax credits, creating open standards for connecting solar power systems to the grid, and giving utilities the ability to include solar power in their rate base.
According to a study by the Solar Energy Industries Association and GTM Research, 878 megawatts (MW) of photovoltaic (PV) capacity and 78 MW of concentrating solar power (CSP) were installed in the U.S. in 2010, enough to power roughly 200,000 homes. In addition, more than 65,000 homes and businesses added solar water heating (SWH) or solar pool heating (SPH) systems. This was double the 435 MW installed in 2009 around the U.S.
According to a 2011 survey conducted by independent polling firm Kelton Research, nine out of 10 Americans support the use and development of solar technology. Eight out of 10 respondents indicated that "the federal government should support solar manufacturing in the U.S. and should give federal subsidies for solar energy". According to the Energy Information Administration, in fiscal year 2013, federal supports and subsidies for solar power amounted to $4.4 billion, over 27% of all federal supports and subsidies for electricity production. This figure does not include state and local spending.
Solar Energy Industries Association and GTM Research found that the amount of new solar electric capacity increased in 2012 by 76 percent from 2011, raising the United States’ market share of the world’s installations above 10 percent, up from roughly 5 to 7 percent in the last seven years.
According to the U.S. Energy Information Administration, as of September 2014 utility-scale solar had sent 12,303 gigawatt-hours of electricity to the U.S. grid. This was an increase of over 100% versus the same period in 2013 (6,048 GWh).
The number of homes with solar systems installed has been increasing rapidly; from 30,000 in 2006 to 400,000 in 2013 with a study by the U.S. Department of Energy predicting the figure could reach 3,800,000 homes by 2020.
Utilities in the United States have led a largely unsuccessful campaign to slow the growth of solar.
Solar thermal power
One of the first applications of concentrated solar was the 6 hp solar powered motor made by H.E. Willsie and John Boyle in 1904.
An early solar pioneer of the 19th and 20th century, Frank Shuman, built a demonstration plant that used solar power to pump water using an array of mirrors in a trough to generate steam. Located in Philadelphia, the solar water pump station was capable of pumping 3000 gallons an hour (25 hp) at that latitude. After seven weeks of testing the plant was disassembled and shipped to Egypt for testing as an irrigation plant.
In 1973, Karl Böer of the University of Delaware built an experimental house called the Solar One, the first house to convert sunlight into energy.
Solar One, the first pilot solar power tower design was completed in 1981. The parabolic trough Solar Energy Generating Systems opened its first unit in 1984, the first major solar thermal plant in the world.
Selected list of plants
Main article: List of solar thermal power stations
The U.S. pioneered solar tower and trough technologies. A number of different solar thermal technologies are in use in the U.S:
The largest solar thermal power plant in the world is the 392 MW Ivanpah Solar Power Facility, in California.
The 64 MW Nevada Solar One uses parabolic trough technology in one of the largest solar plants in the world.
The Ivanpah Solar Electric Generating System is a solar thermal power project in the California Mojave Desert, 40 miles (64 km) southwest of Las Vegas, with a planned gross capacity of 392 megawatts (MW). It deploys 173,500 heliostats each with two mirrors focusing solar energy on boilers located on centralized solar power towers. The facility opened on February 13, 2014.
The Solana Generating Station is a solar power plant near Gila Bend, Arizona, about 70 miles (110 km) southwest of Phoenix, completed in 2013. When commissioned it was the largest parabolic trough plant in the world and the first U.S. solar plant with molten salt thermal energy storage. Built by the Spanish company Abengoa Solar, it has a total capacity of 280 megawatts (MW), which is enough to power 70,000 homes while avoiding around 475,000 tons of carbon dioxide. Its name is the Spanish term for "sunny spot".
The Martin Next Generation Solar Energy Center is a hybrid 75-megawatt (MW) parabolic trough solar energy plant that is owned by Florida Power & Light Company (FPL). The solar plant is a component of the 3,705 MW Martin County Power Plant, which is currently the single largest fossil fuel burning power plant in the United States. Completed at the end of 2010, it is located in western Martin County, Florida, just north of Indiantown.
The Crescent Dunes Solar Energy Project is a 110 MW solar thermal power project near Tonopah, about 230 miles (370 km) northwest of Las Vegas, which was completed in September 2015.
The rapidly falling price of PV solar had led to several projects being abandoned or converted to PV technology. Blythe Solar Power Project converted to a PV project, Rice Solar Energy Project was put on indefinite hold, Palen Solar Project tried to convert to PV but its permits were denied, Hidden Hills Solar Project was suspended in 2013 and later canceled. No major CSP plants remain under construction in the United States.
Within the cumulative PV capacity in the U.S., there has been growth in the distributed generation segment, which are all grid-connected PV installations in the residential and non-residential markets. Non-residential market includes installations on commercial, government, school and non-profit organization properties. Between 2000 and 2013 there had been 2,261 MW of residential solar and 4,051 MW non-residential solar installed. In 2013, there were 1,913 MW installed for these markets; the top 5 states were California, New Jersey, Massachusetts, Hawaii, and Arizona. The residential market had 60% annual growth in 2013. The growth contributing factors were new marketing strategies to partner with retailers to reach more customers, and new financial models including the securitization of residential solar assets. Non-residential PV had a slight growth of 4% in 2013 as the market was recovering from the oversupply in 2012. The future growth will likely come from New York, Arizona, and Colorado.
One of the largest residential solar projects was a 115 kilowatt system on a property in Southern California in 2011. There were many large scale non-residential installations. One of the largest rooftop installations for commercial properties was the 9 MW system of Holt Logistics refrigerated warehouse at the Gloucester Marine Terminal in New Jersey. One of the large scale PV installations in schools was the solar project of San Diego Unified School District with total of 48 sites and aggregated installed capacity of 9.17 MW.
Another type of distributed generation implemented by utility company is the world's first grid-connected pole-attached solar panels of Public Service Enterprise Group in New Jersey. More than 174,000 PV panels are mounted on utility poles along streets of New Jersey with aggregated capacity of 40 MW.
In the United States, 2,106 MW of PV was installed in the 4th quarter and 4,751 MW of PV installations were completed in 2013. Abengoa's 280 MWac of CSP project was brought online in the 3rd quarter and Genesis Solar's first phase of 125 MWac was brought online in the 4th quarter of 2013 bringing the total to 410 MWac for the year and 918 MWac total. Ivanpah is already completed during the first quarter of 2014 the current world's largest CSP power plant is 392 MWac and brings the total to 1310 MWac. The 110 MWac Crescent Dunes project started commissioning during February. The 250 MWac Mojave solar, second phase 125 MWac Genesis Solar, and Tooele Army Depot Solar's 1.5 MWac power plant are all expected to come online in 2014. The A total of around 9.5 GW of solar PV and CSP capacity is expected to come on-line in 2016, more than any other source.
The amount of electricity a unit is capable of producing over an extended period of time is determined by multiplying the capacity by the capacity factor. The capacity factor for solar photovoltaic units is largely a function of climate and latitude. The National Renewable Energy Laboratory has calculated that the highest statewide average solar voltaic capacity factors are in Arizona, New Mexico, and Nevada (each 26.3 percent), and the lowest is Alaska (10.5 percent). The lowest statewide average capacity factor in the contiguous 48 states is in West Virginia (17.2 percent).