When the blackout hit last summer, millions of Michigan residents sweltered for more than two days in the dark.
Restaurants and groceries had to throw out spoiled food. Businesses were forced to shut down for days. And local governments were unable to do much as water systems lost pressure.
The Chamber of Commerce in Detroit and a University of Michigan researcher say the blackout cost $220 million in lost wages.
State regulators found no evidence that Michigan utilities or transmission operators were responsible for the blackout. But they've still taken steps to make sure those companies are doing all that they can to prevent a similar blackout in the future.