SunPower Corp. (SPWR), the second-largest U.S. solar-panel maker, is testing power-storage systems in three countries to complement its residential systems, its chief executive officer said.

The company is evaluating batteries in Germany, Australia and California and expects to have a product to sell to customers within the next couple of years, Chief Executive Officer Tom Wernersaid today in an interview at Bloomberg’s New York headquarters.

Adding batteries to residential solar systems would let people power their homes at night with electricity generated during the day, decreasing demand for energy from the grid and creating a threat to utilities’ revenue, Werner said. California will require utilities to use storage by 2020 and Germany introduced incentives in May to promote wider use of the technology.

“In the near term, we’re driven by policy,” he said. “In the long-term it’s economics.”

The company, based in San Jose, California, gets at least 25 percent of its revenue from photovoltaic panels that end up on consumers’ rooftops.

SolarCity Corp. (SCTY), which provides rooftop solar systems, began offering lithium-ion battery storage units made by Tesla Motors Inc. (TSLA) last week.