Diversity factor formula
Diversity factor = sum of individual maximum demands ÷ coincident system maximum demand.
The numerator is built from the separate peak values entered for each load group. The denominator is the system's coincident maximum, which is the demand observed when the groups are considered together.
Why diversity can be greater than 1
Individual groups can reach their own peaks at different times. Adding those separate maxima can therefore produce a number greater than the system's single coincident peak. That is the characteristic relationship measured by diversity factor.
Worked example
If four groups have maximum demands of 40, 30, 25 and 20 units, their sum is 115 units. If the coincident system maximum demand is 80 units, diversity factor is 115 ÷ 80 = 1.4375.
Group contribution
The tool also expresses each entered group as a percentage of the sum of individual peaks. This helps identify which group contributes most to the numerator, while remembering that contribution to the sum of individual peaks is not the same as contribution to the coincident peak.
Data quality considerations
Use consistent measurement periods and compatible load definitions. Do not mix short-duration equipment peaks with a long-duration system maximum without understanding how the data were derived.
Limitations and safety
Diversity factor is an analytical relationship, not a blanket sizing allowance. Engineering decisions should consider the actual measurement data, project assumptions, equipment ratings and applicable requirements.
Frequently asked questions
Can diversity factor be less than 1?
With correctly defined individual maximum demands and coincident system demand, the sum of individual maxima should not be lower than the coincident system demand on the same basis.
Is diversity factor the inverse of coincidence factor?
When both are defined from the same quantities, they are reciprocals: coincidence factor is coincident demand divided by the sum of individual maximum demands.
Why does the system peak need to be coincident?
Because the comparison is intended to distinguish separate individual peaks from the peak that actually occurs when the whole system is considered at once.