Demand Factor: Load Before and After Diversity
Demand factor is the ratio of the maximum demand used in a load calculation to the connected load for the system, feeder, service or portion being calculated.
Demand factor is often treated like a discount button. It is not. It belongs inside a named load-calculation method, with specific loads included before the factor and other loads handled separately afterward.
Connected load versus demand load
Connected load is the raw total before diversity is recognized. Demand load is the value carried forward after the selected calculation method applies its permitted factor or step.
That distinction is why a service calculation can be smaller than the sum of all appliance nameplates without pretending the nameplates are wrong.
Where dwelling demand factors fit
In dwelling calculations, demand factor normally appears after the eligible general-load subtotal is assembled. The method decides which loads enter that subtotal.
Heating, cooling and some newer equipment categories can be handled after or outside that subtotal, so copying one factor onto every line item can understate the result.
Existing services need the same discipline
For additions to an existing dwelling, demand factor helps answer whether the service has capacity after the new load is included.
The calculation still has to show the existing service rating, the added load, any listed load-management limit and the revised calculated demand.
Where the Term Decides Something
Four points in the work where the figure is the answer to a question, not vocabulary.
Sizing a dwelling service
Demand factors let the load calculation carry a realistic service demand instead of assuming every lighting, receptacle and appliance load runs at full nameplate at the same instant.
Adding load to an existing panel
When EVSE, heat-pump equipment or a large appliance is added, an existing-dwelling calculation uses demand-factor logic to compare the revised demand with the installed service.
Preparing a permit calculation
A reviewer needs the connected-load subtotal, the demand step applied and the resulting volt-amperes. A final amp value without those line items is hard to verify.
Avoiding branch-circuit misuse
Demand factor does not reduce the conductor or OCPD required for a specific branch-circuit load unless the rule for that circuit type explicitly allows it.
Which Figure to Use
Reading the term correctly in practice.
Start with connected load
List the loads at the values the method requires before applying any factor. Demand factor is applied to a defined subtotal, not to a guessed panel capacity.
Stay inside one method
Do not mix optional-method dwelling factors with standard-method line items. Pick the method the calculation is using and keep the order consistent.
Keep HVAC separate when required
In the optional dwelling workflow, the general-load demand step and the heating-or-cooling selection are separate decisions.
Separate demand from continuous load
Demand factor reduces a calculated load where permitted. Continuous-load rules can still require conductors and OCPDs at 125 percent for a specific circuit.
FAQs
What is the demand factor formula?
Is demand factor the same as diversity factor?
Can I apply a dwelling demand factor to every load?
Does demand factor reduce an EV charger branch circuit?
Calculated against the NEC 2023 edition using Article 220, 220.82, 220.83. Confirm the edition adopted by your AHJ, which may differ and may carry local amendments.
Not covered by this tool
- Branch-circuit conductor sizing unless a circuit-specific rule permits demand treatment.
- Equipment nameplate MCA, MOCP or listing instructions.
- Local utility service rules and AHJ forms.
Data last verified