Commercial Elevator Load Calculator

A commercial elevator load calculation starts by converting the stated Motor output power (kW) into the electrical power the supply must deliver. The calculator then applies Power factor (PF) and the entered Duty factor (%) to produce two early-stage planning values:

• Duty-adjusted apparent power (kVA) for preliminary load review
• Duty-adjusted current (A) for initial feeder, raceway, and voltage-drop screening

These values help quantify the electrical demand associated with an elevator drive motor before equipment-specific data is available. They can support an early review of service capacity, distribution loading, approximate feeder routing, raceway space, and preliminary voltage-drop exposure on a long run to the controller.

The result is not a conductor ampacity, breaker size, or final elevator feeder rating. Those selections require the actual elevator motor-controller and driving-machine information, along with the applicable electrical and elevator-code requirements.

Related planning: Motor Current Calculator, Commercial Load Calculator, and Feeder Load Calculator.

Motor Input Power

The mechanical output at the motor shaft is not the same as the electrical input drawn from the source. Efficiency (%) accounts for the motor’s electrical and mechanical losses.

\(\displaystyle \text{Input power (kW)} = \frac{\text{Motor output power (kW)}}{\text{Efficiency} / 100}\)

A 20 kW motor with 90% efficiency requires more than 20 kW from the electrical system:

\(\displaystyle \frac{20}{0.90} = 22.2222\text{ kW}\)

The calculator reports this as Input power: 22.2222 kW.

Input kW is useful for a preliminary electrical load review because it expresses the real power delivered to the motor and its losses. It does not yet represent apparent power or line current.

Power Factor and Duty Factor

AC conductors, switchgear, transformers, and distribution equipment respond to apparent power, expressed in kVA, as well as real power in kW. The calculator converts input kW to kVA with the entered Power factor (PF).

\(\displaystyle \text{Apparent power before duty adjustment (kVA)} = \frac{\text{Input power (kW)}}{\text{Power factor}}\)

The Duty factor (%) is then applied to the apparent-power result:

\(\displaystyle \text{Duty-adjusted apparent power (kVA)} = \left( \frac{\text{Input power (kW)}}{\text{Power factor}} \right) \times \frac{\text{Duty factor}}{100}\)

For elevator screening, the duty factor represents the explicit operating fraction entered for the calculation. It is not a substitute for an applicable demand factor, a motor-duty requirement, a controller nameplate rating, or a manufacturer’s load data.

A lower power factor increases kVA for a given input kW. A lower entered duty factor reduces the calculator’s duty-adjusted kVA and current values. Neither adjustment establishes final conductor ampacity or overcurrent protection.

Duty-Adjusted Current

The calculator uses the entered RMS voltage (V) to convert duty-adjusted apparent power to current.

For a balanced three-phase elevator supply:

\(\displaystyle \text{Duty-adjusted current (A)} = \frac{\text{Duty-adjusted apparent power (kVA)} \times 1000} {\sqrt{3} \times \text{RMS voltage (V)}}\)

For single-phase arithmetic, the phase multiplier is 1, so the denominator is the entered RMS voltage without the square-root-of-three factor. This current is useful during early coordination work. It can be compared against the capacity assumptions for a distribution section and used to identify whether a proposed route may require closer voltage-drop review, larger raceway space, or a different feeder arrangement.

It is not automatically the current used to select AWG or kcmil conductors. Final conductor selection must account for the governing calculated or nameplate load, terminal rating, insulation temperature rating, ambient-temperature correction, adjustment factors for current-carrying conductors, installation method, and equipment listing.

Calculation Example

The following screen values describe a 20 kW elevator motor on a 480 V balanced three-phase system:

Field	Entered value
Motor output power (kW)	20
RMS voltage (V)	480
Power factor (PF)	0.85
Efficiency (%)	90
Phase model	Balanced three-phase
Duty factor (%)	50

First, convert shaft output to electrical input:

\(\displaystyle \text{Input power} = \frac{20}{0.90} = 22.2222\text{ kW}\)

Next, convert input kW to apparent power and apply the 50% duty factor:

\(\displaystyle \text{Duty-adjusted apparent power} = \left( \frac{22.2222}{0.85} \right) \times 0.50 = 13.0719\text{ kVA}\)

Finally, calculate three-phase line current at 480 V:

\(\displaystyle \text{Duty-adjusted current} = \frac{13.0719 \times 1000} {\sqrt{3} \times 480} = 15.7230\text{ A}\)

Result	Value
Input power	22.2222 kW
Duty-adjusted apparent power	13.0719 kVA
Duty-adjusted current	15.7230 A
Power factor used	0.85 PF
Efficiency used	90%

The 15.7230 A result is the calculator’s duty-adjusted three-phase current for the stated values. It provides a starting figure for electrical planning, not a final branch-circuit or feeder ampacity.

Elevator Feeder Verification

Commercial elevator electrical design requires information that an output-kW calculation cannot establish. Confirm the driving-machine motor and controller nameplate data, controller configuration, connected auxiliary loads, supply characteristics, and elevator manufacturer requirements before selecting conductors, disconnects, overcurrent protective devices, or equipment ratings.

Elevator installations are addressed by NEC Article 620, while motor branch-circuit and feeder protection is coordinated with Article 430 requirements. Elevator feeder and branch-circuit conductor ampacity can be based on motor or controller nameplate information and connected loads, not simply on a calculated duty-adjusted current.

Verify the following separately:

• Motor-controller and driving-machine nameplate current ratings
• Starting current, acceleration characteristics, and controller type
• Regenerative operation, harmonic effects, and power-quality requirements where applicable
• Feeder and branch-circuit conductor ampacity, including AWG or kcmil selection
• Terminal rating, insulation temperature rating, correction factor, and adjustment factor application
• Raceway fill, conductor count, grounding and bonding requirements, and routing conditions
• Voltage drop under the relevant operating condition rather than only the duty-adjusted planning current
• Disconnecting means, short-circuit and ground-fault protection, overload protection, and selective-coordination requirements where applicable
• AHJ requirements and the elevator manufacturer’s documented installation data

ASME A17.1/CSA B44 establishes elevator and escalator safety requirements, while electrical equipment associated with elevator systems is subject to its own applicable listing and installation requirements.