One of the state's largest electric utilities is no longer releasing customers to buy power from its competitors. State law allows the major utilities to hang onto their remaining customers once 10% have moved to an alternative supplier. Jackson-based Consumers Energy notified its customers and state regulators last week that it's reached its cap. It won't be releasing any more customers, which are typically large commercial operations and school districts. The utilities say the 10% cap is necessary to ensure financing for the big power plants they need to build to meet Michigan's future energy needs. But critics of the law say it's responsible for Michigan's electric rates being higher than surrounding states.