A method for forecasting a start period for a combined cycle power generation system including a gas turbine engine, a steam turbine and a computer control system, the method including: inputting a desired time at which the power generation system is to reach a dispatchable load; inputting a current value of a predetermined operational condition of the power generation system; the computer control system retrieving historical data relating the predetermined operational condition to prior start periods of the power generation system or a similar power generation system; the computer control system executing an algorithm which generates a forecasted start time based on the desired time, current value and the retrieve data, wherein the power generation system is predicted to reach the dispatchable load at the desired time when started at the forecasted start time, and the computer system outputting the forecasted start time to the output device.