The approvals bring to 50 the number of utility-scale renewable energy proposals and associated transmission the US Interior Department has approved since 2009.

They include 27 solar, 11 wind and 12 geothermal projects.

Of those, 13 are already in operation, including the Ivanpah Solar Electric Generating System, a 377MW solar thermal plant that started commercial operations delivering power to California's electricity grid last week.

The first project of the two recently approved is the 300MW Stateline solar farm project, which will be built in San Bernardino County, California.

The photovoltaic plant will be built on about 682 hectares about 3km from the California-Nevada border and will connect to a 4km 220-kilovolt line.

The second project is the 250MW Silver State South solar project located near Primm, Nevada on about 970ha.

It will be located next to the 50MW Silver State North project, the first solar plant on US public lands to deliver electricity to the grid.

Silver State South will also use photovoltaic panels.

Both projects have been proposed by First Solar and have commitments from Southern Edison to purchase the project's output for 20 years.