In the multiplicative seasonal method, the average value of the
yearly demand is calculated, and the forecasts are developed using
the formula:-
Forecast=Seasonality Factor*Average Demand
For Years 1-4, Seasonality Factors are calculated by using the
formula:-
Seasonality Factor=Quarterly Demand/Average Demand
The average seasonality factor of years 1-4 will be used for
Year 5,i.e,
S.F. for Q1Y5 (Quarter 1 of Year 5)=(Sum of S.F. for
Q1Y1,Q1Y2,Q1Y3 & Q1Y4)/4
All the values are tabulated below:-
| Quarter |
Y1 |
S1 |
Y2 |
S2 |
Y3 |
S3 |
Y4 |
S4 |
Y5 |
S5 |
| 1 |
102.1 |
0.752 |
93.6 |
0.740 |
120.6 |
0.785 |
107.7 |
0.773 |
140.120 |
0.763 |
| 2 |
129.4 |
0.953 |
119.9 |
0.948 |
142.5 |
0.927 |
131.2 |
0.942 |
173.207 |
0.943 |
| 3 |
142.9 |
1.053 |
136.5 |
1.079 |
169.9 |
1.106 |
149.1 |
1.071 |
197.899 |
1.077 |
| 4 |
168.6 |
1.242 |
156.1 |
1.234 |
181.6 |
1.182 |
169 |
1.214 |
223.775 |
1.218 |
| Total |
543 |
506.1 |
614.6 |
557 |
735 |
| Avg. |
135.75 |
126.525 |
153.65 |
139.25 |
183.75 |
where, S1,S2,S3,S4 and S5 are SF for Years 1-5.
The forecast for quarter 1 is 140.1 MW.
