What Diversity Factor Is
Diversity factor is a measure used in electrical design to reflect that not all connected loads operate at their maximum at the same time. It is defined as:
– Diversity factor = (Sum of individual maximum demands) ÷ (Maximum demand of the whole system)
Because the combined system peak is usually lower than the sum of every load’s peak, the diversity factor is typically greater than 1.
Why Diversity Factor Matters
Diversity factor is essential for sizing electrical infrastructure economically and safely:
– Prevents over-sizing cables, breakers, transformers, and switchgear
– Helps estimate realistic maximum demand (kW/kVA) of a site
– Supports planning for expansions (additional chargers, more bays)
– Reduces unnecessary grid upgrade costs by using realistic simultaneity assumptions
Diversity Factor in EV Charging
EV charging can have lower diversity than many traditional building loads because charging sessions can overlap (especially in depots where many vehicles plug in after shifts). That means you must be careful: diversity may be limited unless you apply load management.
Typical contexts:
– Destination charging: higher diversity (arrivals spread out, different dwell times)
– Workplace charging: moderate diversity (arrival clustering in morning)
– Depot charging: often low diversity (simultaneous plug-in after route return) unless actively controlled
– Fast charging hubs: diversity depends on traffic patterns but single sessions can be very high power
Diversity Factor vs Demand Factor
These two are often mixed up:
– Demand factor = (Maximum demand of a system) ÷ (Total connected load)
(Usually < 1)
– Diversity factor = (Sum of individual maximum demands) ÷ (Maximum demand of the whole system)
(Usually > 1)
They are related but describe different perspectives.
How It’s Applied in Design
Engineers use diversity factor when calculating:
– Main feeder and transformer sizing
– Distribution board (DB) ratings and feeder circuit grouping
– Voltage drop and thermal loading assumptions
– Site connection capacity planning with the DNO
For EV sites, many designers pair diversity assumptions with dynamic load management so that the system peak is enforced rather than guessed.
What Influences Diversity Factor
Diversity depends on real usage patterns and control rules:
– Number of chargers and vehicles (larger fleets can increase simultaneity)
– Arrival and departure clustering (shift-based operations)
– Tariffs (cheap off-peak can concentrate charging)
– Load management policies (site power caps, priority rules)
– Vehicle battery sizes and required energy per session
Common Pitfalls
– Assuming high diversity for depot fleets (often wrong without smart charging)
– Using generic diversity factors without validating operational patterns
– Ignoring seasonal and operational changes (new routes, more vehicles)
– Not considering peak coincidence with building loads (warehouse refrigeration, HVAC)
Related Terms for Internal Linking
– Demand factor
– Simultaneity factor
– Maximum demand
– Load management
– Depot power management
– Distribution board (DB)
– Grid connection