(Bloomberg) -- Sunnova Energy International Inc. says the most important step U.S. Congress can take to support solar power is to extend a federal tax credit on investments in the industry.

“The best thing that D.C. can do for solar is to pass the tax credit package,” said Meghan Nutting, executive vice president of government and regulatory affairs at Sunnova, one of the biggest U.S. residential solar companies.

The program, which is set to expire in 2024, offers a 26% tax credit for systems installed between 2020 and 2022 and a 22% credit for those installed in 2023. Nutting makes the case as a federal initiative known as the Clean Electricity Performance Program that encourages utilities to shift away from fossil fuels is likely to get stripped from broader budget plans.

Of all the clean energy proposals that Democrats have introduced during budget negotiations, a 10-year, 30% extension of investment tax credits would stimulate the most growth for U.S. solar and trigger the largest reduction in emissions, said an Oct. 7 report by the Washington-based research firm Resources for the Future.

Solar shares climbed on Tuesday, suggesting that investors are confident the upcoming budget bill will include an extension of the tax credit program. Sunrun Inc., the largest residential solar company in the U.S., gained as much as 8.7%, SunPower Corp. soared as much as 12% and Sunnova was up as much as 8.3%.

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