SolarCity, the solar energy system installer that is planning to build a huge factory in Buffalo through its acquisition of solar panel manufacturer Silevo, was far and away the largest residential installer in the country during the spring.

A new report by analysts at Greentech Media found that SolarCity accounted for almost 3 in 10 residential solar energy systems that were installed across the country during the second quarter. SolarCity’s 29 percent market share was more than three times bigger than the 9 percent share of its nearest competitor, Vivint Solar, the report said. The report sheds light on the strong market position held by SolarCity, which will play a key role in Gov. Andrew M. Cuomo’s Buffalo Billion economic-development initiative with its plans to build a massive factory in South Buffalo that will be one of the largest solar panel production facilities in the world.

SolarCity agreed last month to buy Silevo, a California-based manufacturer of high-efficiency solar panels, in a deal that could be worth as much as $350 million. SolarCity executives immediately said they planned to vastly expand on Silevo’s plans for its factory in the RiverBend development on the old Republic Steel site in South Buffalo, boosting its proposed annual capacity from being able to make enough solar panels to produce 200 megawatts of electricity to 1 gigawatt, or 1,000 megawatts.

With the expansion, the Buffalo factory now is expected to provide well over 1,000 jobs, rather than the 475 initially forecast.

SolarCity’s first-quarter market share was higher than its 27 percent share of the market during all of 2013 but was less than its record market share of 33 percent, which it achieved last summer, the report found. The report also said the market for residential solar energy systems has been growing rapidly, expanding by 38 percent over the last year to more than 230 megawatts in the first quarter.

GTM Research analysts said they expect the U.S. residential solar market to top the 1 gigawatt mark this year. The analysts said the growth in the solar market is due to a 28 percent drop in the average cost of a solar energy system over the last three years, caused by falling equipment prices and lower financing costs that have made solar systems more affordable. That has made the solar industry less dependent on government incentives to be competitive in some states.

The report said that more than half of the residential installations in California and Arizona were done without state incentives during the first quarter, although those systems still were eligible for a 30 percent federal tax credit.