Solar Energy Generating Systems (SEGS) is a concentrated solar power plant in California, United States. With the combined capacity from three separate locations at 354 megawatt (MW), it was once the world's second largest solar thermal energy generating facility, until the commissioning of the even larger Ivanpah facility in 2014. It consisted of nine solar power plants in California's Mojave Desert, where insolation is among the best available in the United States.

SEGS I–II (44 MW) were located at Daggett (34°51′45″N 116°49′45″W); they have been replaced with a solar photovoltaic farm.

SEGS III–VII (150 MW) were installed at Kramer Junction (35°00′43″N 117°33′32″W); all five SEGS have undergone demolition.^[1][2][3]

SEGS VIII–IX (160 MW) are located at Harper Lake (35°01′55″N 117°20′50″W).^[4] NextEra Energy Resources operates and partially owns the plants located at Kramer Junction. On January 26, 2018, the SEGS VIII and IX at Harper Lake were sold to renewable energy company Terra-Gen, LLC.

A tenth plant (SEGS X, 80 MW) had been in construction and SEGS XI and SEGS XII had been planned by Luz Industries, but the developer filed for bankruptcy in 1992, because it was unable to secure construction financing.^[5] The site of SEGS X was later licensed for a solar photovoltaic farm, Lockhart Solar PV II.^[6]

Most of the thermal facilities were retired by 2021,^[7] and photovoltaics were built on the same sites.

Before retirement and replacement of SEGS I-VII with solar photovoltaics, the plants had a 354 MW net (394 MW gross) installed capacity. The nameplate capacity, which operating continuously, would dеliver the samе net power output, coming only from the solar source was around 75 MWe —, representing a 21% capacity factor. In addition, the turbines could be utilized at night by burning natural gas.

NextEra claimed in 2009 that the solar plants could power 232,500 homеs (during the day, at peak power) and displace 3,800 tons of pollution pеr year that would have been produced if the electricity had been providеd by fossil fuels, such as oil.^[8]

The facilities had a total of 936,384 mirrors and cover more than 1,600 acres (647.5 ha). Lined up, the parabolic mirrors would have extended over 229 miles (369 km).

As an example of cost, in 2002, one of the 30 MW Kramer Junction sites required $90 million to construct, and its operation and maintenance cost was about $3 million per year (4.6 cents per kilowatt hour).^[9] With a considered lifetime of 20 years, the operation, maintenance and investments interest and depreciation triples the price, to approximately 14 cents per kilowatt hour.^{[citation needed]}

The installation uses parabolic trough, solar thermal technology along with natural gas to generate electricity. About 90% of the electricity is produced by the sunlight.^{[citation needed]} Natural gas is only used when the solar power is insufficient to meet the demand from Southern California Edison, the distributor of power in southern California.^[10]

The SEGS power plants were built by Luz Industries,^[11][12] and commissioned between December 20, 1984 and October 1, 1990.^[13] After Luz Industries' bankruptcy in 1991 plants were sold to various investor groups as individual projects, and expansion including three more plants was halted.^[5]

Kramer Junction employs about 95 people and 45 people work at Harper Lake.^{[citation needed]}

In February 1999, a 900,000-US-gallon (3,400 m³) mineral oil storage tank exploded at the SEGS I (Daggett) solar power plant, sending flames and smoke into the sky. Authorities were trying to keep flames away from two adjacent containers that held sulfuric acid and sodium hydroxide. The immediate area of 0.5 square miles (1.3 km²) was evacuated.^[34]