Energy system depict a considerable variation in the demand  necessary for system planing and load, to know the total energy requirement and the duration of various loads. the area under a chronological load curve gives the energy consumed during the 24 hours meant of all the load of chronological curve is a descending order.
Thus it shows the total no. of hours for which a particular load lost
during the day the day area under the load direction curve is equal to the area. Since the curve are generally of regular shape the area can be determined graphically.
According to the diagram at starting load the intercept some hours and at load some distance intersect total load hours and these intercept are plotted accordingly at minimum load. the intercept cover the hole period of 24 hours.
Any point on load duration curves gives the no. of hours during 24 hours during which the give load and higher load exist.
If the loads work constants during 24 hours both the chronological and similar and rectangular i shape. The load duration curve plotted for 8760 hours is known as the early load duration curve.

Demand factor

It is the ratio of maximum load to the connected load. Simply we can say that the ratio of maximum demand and connected load are called demand factor.