It was inevitable. Angry Nevadans have now turned to the courts to battle new fees for solar panels.

Last week, solar customers John Bamforth and Stanley Schone filed a class action lawsuit alleging that utility NV Energy provided false information to the state’s regulator, which recently approved added fees for solar customers in the state. The class includes close to 15,000 solar customers in Nevada.

The complaint accuses NV Energy, which is owned by Warren Buffett’s Berkshire Hathaway Energy, of trying to maintain a monopoly in the state by crippling the new solar market. It also alleges that the utility misled solar customers who bought solar panels under the previous rate system and that the utility committed “consumer fraud.”

The contention over the new solar fees has grown increasingly heated since the state regulator approved the rate hike at the end of last year. Last week, thousands of angry protestors crowded around the regulator’s Las Vegas headquarters during its first meeting to address the added fees.

Celebrity actor Mark Ruffalo attended the rally and riled up the crowd by shouting: “Let’s make life uncomfortable for them. For the Governor. For the PUC. Because they’re wrong!” Democratic presidential candidate Bernie Sanders also stood in solidarity with the state’s solar customers by tweeting his support last week.

Actor Mark Ruffalo addresses a protest over new solar fees in Las Vegas. Fortune, Katie Fehrenbacher

While utilities all over the country have been struggling to figure out how to manage customers’ solar panels, Nevada’s situation stands out. That’s because the rate hike doesn’t just apply to new solar customers, but also to home owners who bought solar panels years ago.

Some of these customers spent tens of thousands of dollars under the expectation that the energy generated by the panels would pay for the system over a certain amount of time. But with the added fees, many of the solar panel systems will take far longer to pay for themselves.

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Plaintiff Bamforth spent $36,470 on his solar panels, while plaintiff Schone spent $42,000 on his panels. Both say that they would have never bought the panels if they knew the rates were going to change substantially. The new rates add 40% to their monthly bills, while reducing the amount they get paid for the solar energy their panels produce by 18%.

NV Energy has defended the regulator’s decision to boost the rates because its says non-solar customers have been unfairly paying more than their fair share for maintaining the power grid.

A spokesperson from NV Energy said the company does not comment on litigation.