I have a commerical customer who is wanting a control system, but he is wanting me to give him some kind of enegry analysis to see how long it will take to pay for itself. He gave me all eletric and gas bill for the last six months. I went to the facility and got all the hvac equipment data along with FLA data for each unit and the btu for all the furnaces. They have several split systems with twin furnaces for the most part. What is the best way to come up with a figure to tell tem that a control system will save them money by setting a agressive setback during unoccuppied periods and so on. Any input is greatly appreciated