A method of predicting emissions that may include the steps of: determining a first capacity for emissions during a sliding window of time; determining a used capacity for emissions during the sliding window of time; and determining an available capacity for emissions by calculating the differential between the first capacity and the used capacity. The emission violation may be an opacity emission violation. The first capacity may be the average opacity level available to a fossil fuel fired power plant over the sliding window of time before the opacity emission violation occurs.