Maximum Demand Calculator
Coincident maximum demand from connected load, demand factor and diversity factor. With the formula, a worked example and typical values.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
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About this calculator
This page calculates maximum demand and maximum demand from connected load, demand factor, diversity factor and power factor. Change any value or its unit and the result updates. The steps below show the working for the default values, so you can check each line against your own method.
Limits of this calculator
Use factors from your project specification or standard; the defaults are only examples.
Cross-check: 15 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Indicative
Indicative. Estimation only; further engineering checks are required. Basis: Demand-factor estimate.
What this calculator checks
- The arithmetic of the simplified model for the values you entered.
What remains unverified
- Whether the simplifying assumptions listed on this page hold for your case.
- Any standard, manufacturer or site data. Treat the result as an estimate and confirm it by a further engineering check.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | Not applicable: Demand and diversity factors depend on the adopted wiring code, occupancy and utility rules. The calculator accepts user-defined factors and does not implement a specific standard method. |
| Standard review state | Not applicable |
| Scope-screening note | not recorded |
| Cross-check test cases | 15 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Indicative |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Connected load | 500 kW |
| Demand factor | 0.7 |
| Diversity factor | 1.2 |
| Power factor | 0.9 |
- MD = 500 × 0.7 / 1.2 = 291.67 kW
- S = 291.67 / 0.9 = 324.07 kVA
Assumptions
- Demand factor = max demand ÷ connected load for each group
- Diversity factor ≥ 1 reflects groups peaking at different times
Use factors from your project specification or standard; the defaults are only examples.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Connected load | kW | greater than 0 kW | |
| Demand factor | (number) | greater than 0, up to 1 | |
| Diversity factor | (number) | 1 or more, up to 5 | |
| Power factor | (number) | greater than 0, up to 1 | Rough starting point only. Resistive heating and incandescent loads are 1.0; a fully loaded induction motor is typically 0.8 to 0.88 and falls sharply when lightly loaded; discharge lighting depends on its ballast or driver. For real work use the nameplate or a measured value. |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Maximum demand | kW | Shown to 1 decimal place | |
| Maximum demand | kVA | Shown to 1 decimal place |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
How the result changes with connected load
| Connected load (kW) | Maximum demand (kW) | Maximum demand (kVA) |
|---|---|---|
| 50 | 29.2 | 32.4 |
| 125 | 72.9 | 81 |
| 250 | 145.8 | 162 |
| 500 | 291.7 | 324.1 |
| 1,000 | 583.3 | 648.1 |
| 2,000 | 1,166.7 | 1,296.3 |
| 5,000 | 2,916.7 | 3,240.7 |
Other inputs are the same as in the worked example above.
Standards and further reading
- IEEE Std 1459 (definitions for power quantities under sinusoidal and non-sinusoidal conditions)
Real, apparent and reactive power follow the usual textbook definitions. Tariff and billing rules come from your utility, not from a standard. These are named as background reading. Elecmetric does not embed clause text or rating tables, and the reviewer record for this calculator is separate from this list.
Frequently asked questions
What do I need to enter?
Enter connected load, demand factor, diversity factor and power factor. Change the unit of a value with its selector and the result stays the same.
What does this calculator assume?
Demand factor = max demand ÷ connected load for each group. Diversity factor ≥ 1 reflects groups peaking at different times.
Which calculators should I use next?
Common next steps are Transformer kVA Selection and Generator kVA Selection. The related links at the bottom of this page open them.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 15 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- Demand, Load and Diversity Factor Formulas: Maximum demand, demand factor, load factor and diversity factor formulas with a worked example and a table of maximum…
- Energy Meter Multiplier Formulas: Energy meter formulas: the multiplier of a CT and VT meter
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