Load Duration Curve

A load duration curve is plotted using data on power load (demand) in a system over a period of time. Instead of plotting this data in chronological order, the data is first sorted by size and then plotted from largest (on the left hand side of the x-axis) to smallest (on the right); so a downward sloping curve.

The advantage of such a plot is that it shows quite clearly how often load in the system is above a certain quantity. That’s particularly useful for seeing how often capacity is actually utilised – the answer being that quite a large percentage of the total power plant capacity in the system often exists to deliver just a very few number of hours of peak demand.