Ameren Corp. subsidiary Ameren Illinois Co. is in a showdown with state regulators over the utility's attempt to replace its net metering program with a rebate program that could pay customers less for sending excess distributed solar power onto the grid.

Regulators with the Illinois Commerce Commission on Oct. 1 issued a press release that "urged Ameren to continue to provide full net metering credits to residential solar customers until an audit is completed to protect consumers and avoid disruptions to the solar market."

One day later, on Oct. 2, Ameren said it planned to end its net metering program for new customers.

State law allows an electric utility to end credits for new net metering customers if customer generation equals 5% of the utility's total peak demand. (Docket No. 20-0389). Ameren said the net metering program would be replaced with a program of rebates, the value of which has not been determined.

ICC Chairman Carrie Zalewski said during a meeting that allowing Ameren to end net metering before the commission approved a replacement tariff would violate the legislature's intent to transition smoothly from full retail net metering to a distributed generation rebate.

"Ending net metering without the rebate in place could have a chilling effect on solar sales at a time when the state is working to further decarbonize the grid and increase renewables," Zalewski said. "This could also lead to layoffs in the solar industry at a time when the state is still recovering from an economic downturn."

Three solar advocacy groups on Oct. 5 filed an emergency motion with the ICC asking for an audit of Ameren's net metering program. Ameren said in a filing that it supplied regulators with data supporting its calculation so that regulatory staff can verify it by Oct. 23.

The Solar Energy Industries Association, the Coalition for Community Solar Access and the Illinois Solar Energy Association said in the emergency motion that Ameren is disregarding a directive that commission staff audit Ameren's figures before it ends net metering.

It "is crucial for protecting customers and avoiding unnecessary negative impacts on the solar industry that the Commission not allow Ameren to end retail net metering until the Commission verifies that Ameren has actually met the 5% threshold using the currently applicable methodology." the groups said.