Data compiled for an ongoing federal study of solar-power costs found that the expense for installed systems dropped throughout 2010 and through the first half of this year.
Looking at both residential and commercial installations, the Lawrence Berkeley National Laboratory said costs fell 17 percent in 2010 and another 11 percent through June of this year.
The laboratory, part of the U.S. Department of Energy, has been following the cost of installed systems since 1998 with its "Tracking the Sun" report series.
A big factor in the what consumers pay to install systems has been reduced prices for photovoltaic modules.
“Wholesale PV module prices have fallen precipitously since about 2008, and those upstream cost reductions have made their way through to consumers,” co-author Galen Barbose said in the report.
Other costs have gone down, too, including labor, marketing and other overhead, the report said.
Location and the size of the system installed affected cost, the laboratory said. Costs also were lower for solar systems installed on new homes than for ones retrofitted to existing structures.
