The installed price of solar photovoltaic power systems in the United States is dropping at a rapid rate, a Department of Energy laboratory says. An annual cost-tracking report produced by the department\'s Lawrence Berkeley National Laboratory found the price of residential and commercial photovoltaic systems completed in 2011 fell by roughly 11 to 14 percent from the year before. The price reductions are attributable, in large part, to dramatic reductions in photovoltaic module prices, which have been falling precipitously since 2008, a release from the Berkeley lab said Tuesday. Accompanying costs, such as installation labor, marketing, overhead and current inverters, have also fallen significantly over time, the report\'s authors said. \"The drop in non-module costs is especially important,\" co-author Ryan Wiser of Berkeley Lab\'s Environmental Energy Technologies Division said, \"as these costs can be most readily influenced by local, state, and national policies aimed at accelerating deployment and removing market barriers.\" The median installed price of photovoltaic power systems installed in 2011 was $6.10 per watt for residential and small commercial systems smaller than 10 kilowatts in size and was $4.90 per watt for larger commercial systems of 100 kilowatts or more in size, the report said. The average installed price of a home solar system ranges between $15,000 and $40,000, industry sources said.