I would expect that there is an agency in most states that sets the rules for public utilities just like the Illinois Commerce Commission does in Illinois.
If you are thinking a state agency, you would be wrong.
In most states, regulation for all investor-owned utilities (IOUs) takes place at the state level. There are a few cases where cities regulate the IOUs.
In most states, regulation of customer-owned utilities (COUs) is left to local governmental bodies and elected utility boards. So while there are many exceptions, state commissions generally do not regulate COUs.
In some states, the state commission fully regulates cooperatives. In a few cases the state commission has limited authority over municipal utilities.