Demand factor is the ratio between maximum demand to the connected load on a power system.
The mathematical formula for Demand factor (DF) is:
DF = Maximum Demand/Connected load
Example: A power station has 5 MW load connected to it. While the maximum demand is 3 MW. Find the D.F.
Solution: DF = 3 MW/5 MW = 0.6
The demand factor is always smaller than 1 because the maximum demand on a station is always smaller than connected load.