A load duration curve could be used to help size a cogen plant. The curve shows the number of hours per year the demand is at least the number on the y-axis. (The demand could be say lbs of steam/hr used by an industry (steam host).) This particular curve could say: If you need a minimum demand of 15,0000, you could operate ~6600 hr/yr. You could also operate at a higher number but for a lower number of hours per year.