A view from Nipton, Calif., to a large solar thermal plant.

Ron Handley of Nipton, Calif., looks through the fence surrounding the Ivanpah solar thermal power plant. (Mark Boster / Los Angeles Times / December 5, 2012)

A federal report released this week resolved an obscure argument: Which large-scale solar technology requires the most land?

The inside-baseball question is common among solar power developers. Those who espouse solar thermal technology frequently point out that their "power tower" plants require less land than a large photovoltaic facility using solar panels.

The Energy Department report affirms that, but found little appreciable difference between the two technologies' footprints.

The National Renewable Energy Laboratory in Golden, Colo., found that a utility-scale photovoltaic plant generating enough electricity for 1,000 homes requires 32 acres of land, or an average of 3.7 acres per annual gigawatt-hour, the report said.

Concentrating solar plants — often a field of mirrors that focus sunlight to heat a central tower — require about 3.5 acres per annual gigawatt-hour, according to the report.

By the end of last year, more than 2.1 GW of utility-scale solar power generating equipment had been installed in the U.S. and the study looked at data from 72% of those projects.

Most of the solar power plants in the West are situated on public land.

@julie_cart