WASHINGTON, Feb 4 (Reuters) - Planned cuts to Germany's solar power incentives will probably prompt solar companies to ship excess panels to the United States, pressuring equipment prices here, a top U.S. executive for China's Suntech Power Holdings (STP.N) said on Thursday.

Germany is the top market for photovoltaic solar systems, with about 50 percent of the global market, but the government there is planning to cut prices paid for solar power from roof-mounted systems by 15 percent from April 1.

"Anything that happens in Germany has a ripple effect," Roger Efird, Suntech's managing director for business development in the United States, told the RETECH energy conference.

Solar modules that companies had planned to sell in the German market will probably come to the United States, which could become the biggest solar market by 2013.

Solar companies have struggled in the past year as a glut of supplies pressured module prices by about 40 percent, squeezing profit margins in the nascent industry, and the additional supplies that had been destined for Germany will push U.S. prices even lower.

"I'd say at least another 10 percent drop in pricing, maybe as much as 15 percent," Efird said.

Still, the U.S. solar market could show strong growth this year, he said, potentially doubling from an estimated 500 megawatts that were installed in 2009.

"There is an opportunity that we could hit 1 gigawatt in the United States this year," he said, but that would likely require about 300 MW of large, utility-scale projects.

One megawatt is enough to power about 800 homes.

Suntech, one of the largest solar companies in the world, announced last year it planned to build a new plant in Arizona to expand its business in the United States.