New capital continues to flow into the United States' photovoltaics sector as novel business models open up markets where solar is now competitive with retail electricity rates, according to a new report by NPD Solarbuzz.

Cumulative PV installations in the U.S. hit the 10 GW level in mid-2013 and are on course to double by early 2015, approaching the 20 GW figure by the end of 2014, writes NPD Solarbuzz analyst Michael Barker.

Also buoying the PV business in the U.S. are continuing cost declines and a push by developers to move projects towards completion before a reduction in the federal investment tax credit (ITC).

On the global level, stabilizing component prices and the fact that policy support is decreasing have made downstream players eager to move projects forward rapidly rather than wait for further cost declines or new support mechanisms, Barker says.

According to new research featured in NPD Solarbuzz's North America PV Markets Quarterly report, by the end of 2014, cumulative PV installations in the U.S. will approach 20 GW, representing a doubling of cumulative solar PV capacity within two years, with a compound annual growth rate above 50% since 2006.

Barker points out that while large-scale ground-mounted systems continue to account for the largest share of the U.S. market, all segments are seeing growth. "This strong growth is being assisted by an influx of new capital for centralized and distributed generation (DG), with third-party ownership and system leasing providing a boost to the DG segment."

Solar PV systems are proving increasingly attractive for installers and utility companies as well as institutional investors and private owners and municipalities due to a growing recognition that solar PV systems are a source of relatively low-risk long-term revenues, Barker adds.

However, Barker stresses that there are several risks that could affect PV growth in the U.S., including challenges at the state level to renewable portfolio standard (RPS) targets and net-metering programs and the uncertainty related to the ongoing investigation into Chinese and Taiwanese PV components at the federal level.

"If state-level policies were dramatically scaled-back, or the supply of PV modules was severely restricted, this could prompt a decline in demand or an increase in pricing," he says. While the impact on state-level demand that policy changes would have typically take some time, any change in the trade cases could have a much quicker – and countrywide – impact, Barker adds.