Diversity Factor Calculator — Coincident Demand

Calculate

Mode

Compute: enter Σ and the coincident demand to get the diversity factor. Apply: enter Σ and an assumed diversity factor to get the coincident demand to size against.

kVA is recommended for transformer sizing where power factor varies. kW for real-power sizing. Amperes only when all demands share the same voltage and phase basis.

Demand Inputs

Sum of the individual peak demands for each load in the group. Each load's peak is its own maximum, measured or nameplate; they need not occur simultaneously.

The maximum demand the group actually places on the shared feeder or transformer — measured or estimated as the group's simultaneous peak. Must be ≤ Σ.

Advanced Parameters

Total nameplate or rated load of all connected equipment in the same unit. When entered, the demand factor (D_c ÷ L) is shown for reference only — it does not affect the diversity factor result.

The diversity factor the design assumed for sizing. When entered, the calculator screens the computed DF against this value and reports the impact in demand units. Must be ≥ 1.

Overview

Use this calculator to determine how much demand a group of electrical loads actually places on a shared feeder, transformer, or panel when the fact that their individual peaks do not all occur at the same time is taken into account. It works in two directions: Compute mode takes the sum of the individual maximum demands and the measured coincident maximum demand and returns the diversity factor; Apply mode takes the sum and an assumed diversity factor and returns the coincident demand to size the shared equipment against. Both the diversity factor and its reciprocal the coincidence factor are returned, together with the load diversity — the demand the common point never sees because the peaks are staggered in time.

What to Look at First

When you click Calculate, look at these outputs in order:

  • In Compute mode: the diversity factor and coincidence factor; the load diversity tells you how much demand the common point never sees
  • In Apply mode: the required coincident demand (planning value, rounded up) and the exact calculated demand — size the shared equipment to the planning value
  • The Track B band, if a reference DF was entered: green means the assumption is conservative; amber or red means the real loads are more coincident than assumed and the shared equipment may be undersized
  • The demand factor row, if a connected load was entered — it is shown for reference only and does not affect the diversity factor result
  • If the result is INFEASIBLE, a required field for the active mode is missing; if INVALID-INPUT, check for D_c > Σ, DF < 1, or a coincidence factor entered where a diversity factor belongs

How to Use This Calculator

  1. Select the calculation mode. Compute mode returns the diversity factor from two known demand figures. Apply mode returns the coincident demand from a known demand sum and an assumed diversity factor.

  2. Select the demand unit: kVA, kW, or amperes. Use the same unit for all demand entries. For transformer sizing, kVA is recommended because apparent power governs when the power factor varies across loads. Amperes are valid only when every demand shares the same voltage and phase basis.

  3. In Compute mode, enter the sum of the individual maximum demands and the coincident maximum demand. In Apply mode, enter the sum and the assumed diversity factor. If your reference table gives a coincidence factor instead, enter its reciprocal.

  4. Optionally open the advanced fields. Enter the total connected load to also see the demand factor as a reference quantity. In Compute mode, enter a reference diversity factor to screen the computed result against the sizing assumption.

  5. Read the result. In Compute mode, the diversity factor, coincidence factor, and load diversity are returned. In Apply mode, the required coincident demand — sizing value and exact figure — plus coincidence factor and load diversity are shown.

All input fields are empty by default. Fill in only the fields that apply to your scenario.

Inputs & Outputs

Inputs

  • •Calculation Mode — Options: Compute — calculate diversity factor from two demands, Apply — calculate coincident demand from assumed factor
  • •Demand Unit — Options: kVA, kW, A
  • •Sum of Individual Maximum Demands (Σ)
  • •Coincident System Maximum Demand
  • •Assumed Diversity Factor (DF ≥ 1)
  • •Total Connected Load (optional)
  • •Reference / Assumed Diversity Factor (optional)

Outputs

  • •Result Status
  • •Diversity Factor
  • •Coincidence Factor
  • •Load Diversity
  • •Required Coincident Demand (sizing)
  • •Exact Calculated Demand
  • •Demand Factor (reference only)
  • •Reference Coincident Demand
  • •Coincident Demand Difference

Formula

Compute Mode

DF = Σ (individual maximum demands) / coincident maximum demand
CF = 1 / DF = coincident maximum demand / Σ
Load Diversity = Σ − coincident maximum demand

Apply Mode

Coincident Demand = Σ / DF
CF = 1 / DF
Load Diversity = Σ − coincident demand
Sizing value = coincident demand rounded up to planning step
  kVA/kW: < 10 → nearest 0.1 | 10–100 → nearest 1 | > 100 → nearest 5
  A:      < 100 → nearest 1  | ≥ 100   → nearest 5

Demand Factor (optional, reference only)

Demand Factor = coincident maximum demand / total connected load

Track B — Sizing Assumption Screen (Compute + reference DF)

Reference coincident demand: D_ref = Σ / DF_ref
Deviation: (DF_computed − DF_ref) / DF_ref × 100%
  ≥ 0%        → conservative — sizing assumption holds
  0% to −15%  → marginally below — verify coincident-demand basis
  −15% to −50%→ materially below — re-check shared equipment rating
  < −50%      → undersizing risk — strong demand shortfall

Diversity Factor vs Coincidence Factor

These two are the same information expressed in opposite directions. Diversity factor divides the sum of the individual maximum demands by the coincident maximum demand, so it is always 1.0 or higher. Coincidence factor divides the coincident demand by the summed demands, so it is always 1.0 or lower. One is the reciprocal of the other: a diversity factor of 1.43 is the same situation as a coincidence factor of 0.70.

The practical consequence is straightforward. If a table or a utility document hands you a number below 1.0, it is a coincidence factor. To use it in Apply mode, take its reciprocal and enter that as the assumed diversity factor. The convention note in the result panel reminds you of this each time.

Diversity Factor vs Demand Factor

These are unrelated quantities that share a similar name. Demand factor compares the actual maximum demand to the total connected load, so it measures how much of the installed capacity is in use and is never more than 1.0. Diversity factor compares the sum of individual peaks to the group's coincident peak, so it measures how those peaks overlap and is never less than 1.0.

They are not interchangeable and they are not reciprocals of each other. A panel can have a low demand factor because much of its connected load is idle, and at the same time a high diversity factor because the loads that do run rarely peak together. This calculator uses diversity factor throughout; the demand factor is shown only when you enter a connected load, and only as a reference that takes no part in the diversity-factor calculation.

Coincident Demand from Diversity Factor

When you already have a diversity factor for a load class, the coincident demand follows directly from the sum of the individual maximum demands. For a group of loads whose individual peaks sum to 500 kVA, an assumed diversity factor of 1.6 gives a coincident demand of 500 / 1.6 = 312.5 kVA. That coincident demand, rounded up to a planning value of 315 kVA at a 5 kVA step, is what the shared feeder and transformer are sized to carry, not the full 500 kVA connected sum. Apply mode performs this calculation and also returns the coincidence factor and load diversity for the same case.

How to Use Diversity Factor for Feeder or Transformer Sizing

The reason diversity factor matters for sizing is that a shared feeder or transformer never has to carry the arithmetic sum of every load's peak. Sum the individual maximum demands of the loads on the shared equipment, divide by a diversity factor appropriate to that load class, and size the equipment to the resulting coincident demand. The connected sum overstates what the equipment will ever see, often by a wide margin.

The factor has to suit the actual load group. A figure measured for residential feeders does not describe an industrial shop, a row of EV chargers, or a data hall. Once the equipment is in service, comparing the measured coincident demand against the diversity assumption used to size it is a useful check: if the real loads turn out more coincident than assumed, the coincident demand is higher than the sizing basis and the shared equipment may be short of capacity.

What is the Diversity Factor for Loads

Diversity factor describes the fact that the loads connected to a shared part of a power system rarely reach their individual peaks at the same instant. Ten thermostatically controlled air-conditioning units each draw their rated current at some point during the day, but the moment when all ten run together may never occur. The feeder that supplies them sees a peak lower than the sum of the ten individual peaks, and diversity factor puts a number on that gap.

Formally it is the sum of the individual maximum demands divided by the coincident maximum demand of the whole group, so a diversity factor of 1.4 means the parts, added up, peak forty percent higher than the group ever does at once. The coincidence factor is the same information expressed the other way, as the fraction of the summed peaks that actually coincides. Load diversity is the difference in demand units — the headroom that exists at the common point purely because the peaks are spread out in time.

Diversity factor is the tool utilities and plant engineers use to size shared distribution equipment without paying for capacity that the load shape will never call on. NEC 430.26 recognizes demand reduction for motor feeders and points engineers to the IEEE recommended-practice sources for appropriate factors; the code itself does not tabulate diversity factors, and this calculator does not perform NEC Article 220 demand calculations, which are a separate method.

Key Facts

  • Diversity factor is always 1.0 or higher — the coincident peak of a group can never exceed the sum of the individual peaks.
  • The coincidence factor is the reciprocal of the diversity factor and is always 1.0 or lower.
  • Load diversity — the difference between summed peaks and coincident peak — is the capacity the shared feeder never has to carry because the peaks do not align.
  • Diversity factor and demand factor are unrelated: demand factor ≤ 1, diversity factor ≥ 1; they are not reciprocals.
  • A higher diversity factor means peaks are more staggered, so the coincident demand is much lower than the connected sum.
  • Diversity factor is group-specific; a figure measured for residential feeders does not transfer to industrial process loads, EV charging, or data-centre equipment without its own basis.
  • Because diversity factor is a ratio of two demands in the same unit, it is dimensionless and reads the same in kVA, kW, or amperes.
  • For transformer and apparent-power sizing where the power factor varies across loads, kVA is the safer basis than kW.

Applications

  • Sizing a shared feeder or distribution transformer serving loads with non-coincident peaks.
  • Estimating the coincident demand a panel or substation will actually see rather than the conservative sum.
  • Converting between an assumed diversity factor from a utility planning guide and the coincident demand it implies.
  • Converting coincidence-factor tables into diversity-factor inputs by taking the reciprocal.
  • Checking whether a design diversity assumption is still valid against measured demand.
  • Screening whether an existing service can absorb additional load once realistic peak overlap is accounted for.
  • First-pass demand coordination on industrial and commercial projects before a detailed load study.

Example Calculation

Compute mode example: A switchboard serves a group of loads whose individual maximum demands sum to 500 kW. Metering shows the coincident maximum demand is 350 kW. DF = 500 / 350 = 1.43; CF = 0.700; Load Diversity = 150 kW.

If the design had assumed a reference DF of 1.25, the computed 1.43 is above the reference — the sizing assumption is conservative. The reference implied 500 / 1.25 = 400 kW coincident demand, while the measured basis is 350 kW, leaving 50 kW of headroom against the assumption.

Apply mode example: A feeder serves loads summing to 500 kVA. A utility planning table gives DF = 1.6. D_c = 500 / 1.6 = 312.5 kVA. Planning value (rounded up at 5 kVA step) = 315 kVA. CF = 0.625. Load Diversity = 187 kVA (floor of 187.5). The feeder and transformer are sized for 315 kVA, not the full 500 kVA sum.

Standards & References

  • NFPA 70, National Electrical Code — Article 220 and 430.26
  • NFPA 70 — free online access
  • IEEE Std 3002.2-2018 — Recommended Practice for Conducting Load-Flow Studies and Analysis of Industrial and Commercial Power Systems
  • IEEE Std 100 — The Authoritative Dictionary of IEEE Standards Terms — diversity-factor and coincidence-factor definitions
  • IEEE Std 141 (Red Book) — Recommended Practice for Electric Power Distribution for Industrial Plants
  • IEEE Std 241 (Gray Book) — Recommended Practice for Electric Power Systems in Commercial Buildings

Use the edition adopted by your project, AHJ, or utility planning standard. NEC 430.26 directs the engineer to the IEEE recommended practices for the factor tables; the code itself does not list diversity factors.

Units

Diversity factor and coincidence factor are pure ratios with no units, and they read the same regardless of how the demands are expressed. The demand entries and the load diversity carry the selected unit: kilovolt-amperes (kVA), kilowatts (kW), or amperes (A). Use the same unit for both demand inputs — the ratio only holds when numerator and denominator share a basis.

Electrical demand is an SI quantity; there is no imperial counterpart. A kilowatt is a kilowatt in any region. For motor nameplates given in horsepower, convert to kW first using approximately 0.746 kW per horsepower. Amperes are valid only when every demand shares the same voltage and phase basis; for loads at mixed voltages or across transformer boundaries, work in kVA or kW. For transformer sizing where the power factor varies across loads, kVA is the safer basis.

Limitations

  • This is a preliminary demand-screening calculator, not a substitute for a measured load study.
  • It does not perform NEC Article 220 demand-factor calculations, which are a separate method.
  • It does not size conductors, set protective-device ratings, or check voltage drop.
  • Diversity factor depends on load class, metering interval, season, occupancy, and measurement window — a factor from one context does not carry over to another without justification.
  • Managed or controlled loads such as scheduled EV charging need their own coincidence assumptions.
  • The calculator assumes Σ and D_c share the same load group, time basis, and unit.
  • A coincident current in amperes still needs phase-balance, neutral-loading, and harmonic checks before use for feeder thermal sizing.
  • The demand factor shown when a connected load is entered is for reference only and takes no part in the diversity-factor result.

Common Mistakes to Avoid

  • Entering a coincidence factor (below 1) where a diversity factor belongs — use its reciprocal instead.
  • Confusing diversity factor with demand factor: demand factor is at most 1.0; diversity factor is at least 1.0.
  • Using a diversity factor without documenting its source — it must come from measured data or a defensible load-class table.
  • Applying diversity twice — do not apply a factor to a demand value that already includes a diversity or demand adjustment.
  • Building the demand sum from different time periods or leaving loads out of it.
  • Applying a factor borrowed from an unrelated load class.
  • Mixing demand units, or using amperes across different voltages.
  • Treating the rounded coincident demand as the final equipment rating — it is a minimum sizing basis only.

Frequently Asked Questions

Can a diversity factor be less than 1?
No, not under the convention this calculator uses. Diversity factor is the sum of the individual maximum demands divided by the coincident maximum demand, and the coincident peak can never exceed the sum of the parts, so the value is always 1.0 or higher. If you have a number below 1.0, it is a coincidence factor; enter its reciprocal as the diversity factor.
How is diversity factor different from demand factor?
Demand factor compares the actual maximum demand to the total connected load, so it tells you how much of the installed capacity is being used and is never more than 1.0. Diversity factor compares the sum of individual peaks to the group's coincident peak, so it tells you how much those peaks overlap and is never less than 1.0. They answer different questions and are not reciprocals of each other.
How do I use diversity factor to size a feeder or transformer?
Sum the individual maximum demands of the loads on the shared equipment, then divide by a diversity factor appropriate to that load class to get the coincident demand. Size the feeder and transformer to that coincident demand rather than to the connected sum. Apply mode does this directly: enter the demand sum and the assumed factor, and it returns the coincident demand to size against.
Should I use kW or kVA for diversity factor?
Use kW when real power demand is the sizing basis. Use kVA for transformer and apparent-power equipment sizing, especially when the power factor varies across the loads, since the equipment is rated in apparent power. The factor itself is the same number either way; only the demand and load-diversity figures carry the unit.
Where do diversity factors come from?
From measured demand data for similar installations, or from load-class tables in utility planning guides and the IEEE recommended-practice books. NEC 430.26 recognizes the principle for motor feeders and points to the IEEE 141 and 241 practices for the factors. There is no single universal table; the factor has to suit the actual load class, and a measured value for the specific site is always preferable.
What if my measured diversity factor is lower than the assumed value?
It means the real loads peak more closely together than the design expected, so the coincident demand is higher than the sizing assumption and the shared equipment may be undersized. Enter the assumed value as the reference DF in Compute mode to quantify this — the calculator reports the demand impact in the selected unit.
Can I use diversity factor for NEC Article 220 dwelling or service calculations?
No. NEC Article 220 demand calculations are a separate code method with their own demand factors. This calculator is for diversity and coincidence analysis of load groups, the approach used for utility and shared-equipment sizing. Use a dedicated Article 220 tool for dwelling and service load calculations.
Can I enter demands in amperes?
Yes, as long as every demand shares the same voltage and phase basis, because the ratio only holds when numerator and denominator are measured the same way. For loads at mixed voltages or on opposite sides of a transformer, work in kVA or kW. For sizing where the power factor varies across loads, kVA is the safer choice.

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Electrical Load Calculator

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