(WTVO) — Northern Illinois ComEd customers will begin receiving a $20 every month beginning in June.

The Illinois Commerce Commission announced on April 27 that the carbon mitigation credit, which will be on ComEd bills through May 2023, will save the average customer $237, according to the Chicago Tribune.

The estimated $1.7 billion credit came after legislation was passed to support the three nuclear plants as part of Illinois’ “Climate and Equitable Jobs Act.”

The credit was reportedly not expected when the clean energy bill was enacted last fall.

“It is a surprise,” said David Kolata, executive director of the Citizens Utility Board, a nonprofit Illinois watchdog group. “But the main driver of energy prices being higher is the Russian invasion, and I don’t know if people predicted that.”

The clean energy bill, which was signed into law by Illinois Governor JB Pritzker back in September, requires utilities in Illinois to get 40% of their power from renewable sources by 2030. It also gave funding to the Byron, Dresden and Braidwood nuclear plants as sources for clean energy.

Constellation, which owns the plants, threatened to close Byron and Dresden plants without legislative action, as they were uneconomic. Rising energy prices, as well as Russia’s invasion of Ukraine, made the plants more profitable.

“This was in the bill, because if the nuclear plants don’t need the money, they shouldn’t get the money,” Kolata said. “We’re getting a refund being paid for by the nuclear plants, because they’re earning more than they agreed to.”

Kolta warned that, while customers are currently coming out ahead, the nuclear plant bailout could go back to a ratepayer-funded subsidy in the coming years.

“This unprecedented credit to Illinois consumers further demonstrates the critical role nuclear power plays in providing clean, resilient and reliable energy, while keeping electricity costs affordable for customers. To date, Illinois consumers have not paid a penny to nuclear plants under the law, and instead will be receiving a substantial credit,” Constellation said in a statement.

The credit will begin to appear on ComEd bills in June as a “Carbon-Free Energy Resource Adjustment.” The energy company provides electricity to more than 4 million customers across Northern Illinois.

EDITOR’S NOTE: A prior version of this story incorrectly identified Exelon as the current owner of the Byron and Dresden nuclear plants.