Consumers Energy would have to double the number of wind turbines currently operating in this state to replace the electricity produced by just one of the coal- and gas-fired power plants it intends to close as part of its plans to rely more on renewable sources. The problem, however, is that those additional turbines only spin about one-third of the time, leaving a big energy gap for the households and businesses that rely on the company for their electricity.

According to a recent report from the state Public Service Commission, regulated utilities and their vendors operate 1,107 industrial wind turbines in Michigan. These can produce 1,925.3 megawatts of electricity, but only when the wind is blowing.

Compare that to the Dan E. Karn generation plant in Bay County, which Consumers Energy plans shut down by 2032. Its four coal and two natural gas burners can produce up to 1,946.3 megawatts regardless of wind or weather.

Because the wind only blows intermittently, wind turbines in Michigan have a 36% capacity factor. That is, they can produce 1,925.3 megawatts of electricity just 36% of the time, on average. This means that, theoretically, it would require building another 2,162 wind turbines to replace the Karn coal plant.

But even that would not meet the need, because there is not enough variation in weather across Michigan to ensure that if turbine blades aren’t spinning in one area, they will do so elsewhere. When the blades are not spinning, Michigan’s utilities and the customers who rely on them would have to hope that utilities in other states have extra power available to sell at reasonable rates.

Coal-fired generators provided 37% of Michigan’s net electricity generation in 2018, according to the federal Energy Information Administration. Renewable sources provided 8%, with more than half of that coming from wind turbines.

Consumers Energy retired seven of its coal-fired generation plants in 2016. In June, the company announced it was closing the two coal-fired units at the Karn plant as of 2023.

Consumers Energy recently put representatives on tour around Michigan to promote the company’s plans to rely on intermittent renewable sources for 90% of the electricity its customers need by 2040.

Michigan’s law regulating regional electric monopolies like Consumers Energy and DTE Energy guarantees them a return of around 10% on all their operations. Those operations include tearing down existing power plants and replacing them with new facilities, including renewable source generators.

This story depends on an analysis done by Jason Hayes, the director of environmental policy at the Mackinac Center for Public Policy.