While the cost of installing solar power in the United States has dropped, a federal report finds savings are offset in part by a decline in incentives.

The U.S. government is supporting solar development through its SunShot initiative, which aims to make the renewable technology competitive. The program aims to move solar power capacity from less than 1 percent of the national electricity supply to 14 percent by 2030.

In February, energy consultant group Wood Mackenzie found solar power has evolved from a niche renewable sector to something that's pressuring conventional business models in the utility industry.

The Lawrence Berkeley National Lab surveyed about 80 percent of all U.S. residential and non-residential photovoltaic systems installed through 2014 and found national median installed prices declined 9 percent year-on-year for residential systems, 10 percent for small-scale non-residential systems and 21 percent for larger non-residential systems.

"Preliminary data for the first half of 2015 indicate that installed price declines have persisted into 2015 and are on pace to match those witnessed in recent years," the report found.

The report found some of the savings comes from so-called soft cost reductions, which include things like installation labor and marketing.

The decline in the price of installing solar power, however, has been offset partially by a drop in incentives. The national lab's report found rebates and performance-based incentives provided through state governments and utility companies have dropped off "substantially" from 10 years ago.

While factors depend largely on the particulars, the report finds the decline in incentives equates to at least 70 percent of the corresponding decline in what it costs to have solar power installed.

"This trend is partly a response to installed price declines and the emergence of other forms of incentives, but it has also been a deliberate strategy by program administrators to provide a long-term signal to the industry to reduce costs, and is likely among the many drivers for recent declines in solar soft costs," the report found.