Warren Buffett’s Berkshire Hathaway, which agreed to buy a $2 billion solar farm in California in a deal announced yesterday, may have picked the right time to invest in the industry.

The 550-megawatt Topaz project will qualify for a federal incentive because it began construction last month, and will sell power under a long-term contract that was completed before prices for solar panels fell 44 percent in the last year.

Buffett’s MidAmerican Energy set the deal with First Solar of Tempe, Ariz.

Topaz, which will use First Solar panels, may be the last large solar farm to qualify for the US Treasury Department incentive program, which is set to end this year. It will likely sell power at a higher price than projects that are seeking utility contracts now, said Paul Clegg, an analyst at Mizuho Securities.

Terms weren’t disclosed.

First Solar rose 4.1 percent to $47.99, while Berkshire Hathaway gained 0.7 percent to $118,240.