Define responsibility factor

Responsibility factor (also called contribution factor) of a consumer or consumer class is the ratio of its load at the time of the system (or group) peak to its own maximum demand:

$$\text{Responsibility factor } c_i = \frac{\text{Load of consumer } i \text{ at time of system peak}}{\text{Maximum demand of consumer } i} \le 1$$

For example, a commercial class with a 10 kW peak at noon that draws only 5 kW at the evening system peak has a responsibility factor of 0.5.

The system peak is then $P_{system} = \sum c_i P_{max,i}$, and the coincidence factor of the group is $\sum c_i P_{max,i} / \sum P_{max,i}$.

Significance in distribution design:

• At a load centre with several consumer classes (domestic, commercial, industrial), the class peaks occur at different hours. The load centre peak is the sum of each class peak weighted by its responsibility factor, not their plain sum.
• It is the key input for sizing distribution transformers and feeders in load forecasting (e.g. "5th year contribution factor to peak").
• It identifies which class is responsible for the peak; tariffs (time-of-day pricing) and demand-side measures can then target that class.
• Using correct factors avoids oversizing equipment and reduces capital cost and no-load losses.