The projects use different solar thermal technology and storage options.

Abengoa's Solana plant, which went online in October, is a 250 megawatt parabolic trough plant in Gila Bend, Arizona, with integrated thermal storage.

Brightsource's Ivanpah, expected to enter service by the end of the year, is a 391MW power tower plant in California's Mojave desert. It does not include storage.

Solana and Ivanpah are much larger than solar thermal plants that have previously entered service in the US.

Over the past decade, a few smaller-scale and demonstration solar thermal projects have entered service.

The only other dedicated solar thermal plants larger than 10MW in the US are the series of Solar Energy Generating plants built in California in the 1980s and early 1990s and the Nevada Solar One parabolic trough project completed in 2007.

EIA projects for total solar thermal capacity additions in 2013-14 include six projects for 1257MW with more expected in 2015-16.

However, while these solar thermal capacity additions are significant for the technology they represent only 4% of total expected capacity additions for 2013-14. That is despite solar photovoltaic only meaningfully entering the utility-scale market in the past few years.