The installed cost of solar power systems in the US fell substantially last year and in the first half of this year, according the Department of Energy’s Lawrence Berkeley National Laboratory.

According to the laboratory’s annual PV cost-tracker report, the median installed price of residential and commercial PV systems fell by 11-14% compared to the year before, depending on system size.

The report attributed the installed price reductions to “dramatic” decreases in PV module prices since 2008

It found that the median installed price of PV systems installed in 2011 was $6.10/W for residential and small commercial systems smaller than 10kW in size, and was $4.90/W for larger commercial systems of 100kW or more in size. Utility-sector PV systems larger than 2,000 kW in size averaged $3.40/W in 2011. 

The report also highlighted the considerable falls in “non-module” costs such as labour, balance of systems and marketing.

Report co-author Ryan Wiser of Berkeley Lab’s Environmental Energy Technologies Division said: “The drop in non-module costs is especially important as these costs can be most readily influenced by local, state and national policies aimed at accelerating deployment and removing market barriers.”

According to the report, average non-module costs for residential and commercial systems declined by roughly 30% from 1998 to 2011, but have not declined as rapidly as module prices in recent years.

As a result it said continued “deep” reductions in the price of solar would require an emphasis on lowering the “soft” costs of systems.