This study analyses the un-priced environmental harm caused by generating electricity from fossil fuels in the ECAR control region south of the Great Lakes in 2004 and again in 2015 when the recent Clean Air Interstate Rule will have its full effect. Using existing damage values, we estimate wholesale electricity under-pricing for coal-fired plants at about $40 per MWh in 2004, almost as much again as the $45/MWh actual price. Averaging across all fuels, the price of electricity was more than $30/MWh too low. The under-pricing will still be $18/MWh for coal plants and $15 for all generation sources in 2015, a decade after CAIR was adopted. Recognizing this environmental price ...