Annual duration line
The annual duration curve is a diagram commonly used in the energy industry that shows the power requirement of a supply object based on the respective usage time. The annual duration curve shows how many hours a year a certain service is in demand. This is of practical importance in capacity planning and in the profitability assessment: peaks in demand that occur only a few hours a year are usually covered differently than an almost constant constant demand.
Alternatively, the annual duration curve can also be used to show the utilization of an electricity or heat generator.
In the most common form of an annual duration curve diagram, the number of hours - a maximum of 8760 annual hours - is shown on the abscissa and the performance on the ordinate . In this form of representation, a horizontal year duration line would be the best case, because this means that the demand is always the same. The steeper the line deviates from the horizontal, the more often a system dimensioned for the maximum requirement remains underutilized.