Elevator Motor Power Calculator
Beta Version 1.0 I 30/12/2025
What is this tool?
The Elevator Motor Power Calculator V1.0 calculates peak motor power requirements for elevators according to ASHRAE 90.1 Appendix G (Section G3.9). This is for energy modeling and code compliance work, not actual elevator engineering. If you're specifying a real elevator system, you need structural calculations, traffic analysis, and a whole stack of other things this tool doesn't touch. But if you're modeling a building's baseline energy performance for ASHRAE compliance, this gets you the numbers the standard requires.
The calculator handles three scenarios: single elevators, multiple elevator banks, and baseline-versus-proposed comparisons for demonstrating energy savings.
Download the tool here: Elevator Motor Power Calculator V 1.0
System Requirements
Browser: Any modern browser with JavaScript enabled. Chrome, Firefox, Edge, Safari all work fine.
Network: Not required once loaded. The tool runs entirely in your browser.
Files: Standalone HTML file. No installation, no dependencies, no server needed.
Quick Start
Single Elevator (2 minutes)
The simplest path. You have one elevator, you need one number.
Step 1: Pick a building template or enter specifications manually
Templates cover typical configurations: residential low-rise, office building, hospital, freight elevator. Clicking a template auto-fills all the fields with industry-standard values. Or skip templates and type in your actual specs.
Step 2: Fill in the required fields
Number of stories (including basement): Determines hydraulic versus traction motor
Car weight (kg): Empty elevator car mass
Rated load (kg): Maximum passenger/cargo capacity
Speed (m/s): How fast it moves
Counterweight (kg, optional): Only for traction elevators (>4 stories). Leave blank to use ASHRAE default of car weight plus 40% of rated load.
Step 3: Click Calculate
Results show motor type, efficiencies used, intermediate calculations, and peak motor power in kW. This last number is what goes into your energy model.
Multiple Elevators (5 minutes)
Real buildings have multiple elevators with different specs. This mode handles that.
Step 1: Switch to Multiple Elevators mode using the mode selector at top
Step 2: Click "Add" to create an elevator bank
Modal opens with building templates at the top (same as single mode). Click a template to auto-fill, or enter specs manually. Set "Number of Units" if you have multiple identical elevators (e.g., three passenger banks with the same specs). Give it a name like "Passenger Bank A" or "Service Elevator".
Step 3: Repeat for each elevator type in your building
Step 4: Click "Calculate Total Power"
Results show total peak power across all elevators, count, average power per unit, and a rough annual energy estimate (assumes 60% diversity factor and typical operating hours). The diversity factor accounts for the fact that not all elevators run simultaneously at peak load.
Comparison Mode (5 minutes)
For compliance documentation where you need to demonstrate that your proposed design performs better than the ASHRAE baseline.
Step 1: Switch to Comparison mode
Step 2: Fill in baseline specifications
What ASHRAE G3.9 requires for a building of this type. Usually this means less efficient motor, standard counterweight, etc.
Step 3: Fill in proposed design specifications
Your actual elevator specifications. Might include better counterweight balance, more efficient motors, lighter car weight.
Step 4: Click "Compare Performance"
Results show side-by-side power requirements, motor types, efficiencies, and percentage savings. This goes directly into your compliance documentation showing how much better your design performs than code minimum.
Understanding the Inputs
Number of Stories
Count every level including basements. This single number determines everything else about the calculation.
4 stories or fewer: You get a hydraulic elevator. No counterweight, 58% mechanical efficiency, less efficient motors from Table G3.9.3.
More than 4 stories: You get a traction elevator. Includes counterweight, 64% mechanical efficiency, better motors from Table G3.9.1.
The cutoff is exactly at 4. ASHRAE picked this number based on typical industry practice where hydraulic elevators become impractical above four stories due to jack stroke limitations. Whether your building actually uses hydraulic or traction doesn't matter for baseline modeling. ASHRAE tells you which type to model based on building height.
Car Weight
Mass of the empty elevator car in kilograms. This includes the cabin structure, doors, guide rails, and everything else that moves up and down. Typical ranges:
Small residential: 800-1000 kg
Standard commercial: 1200-1500 kg
Large freight: 1800-2500 kg
If you don't have manufacturer specs, you're guessing. For compliance work, get actual data from the elevator supplier or use the building templates which have industry-standard values.
Rated Load
Maximum passenger and cargo weight the elevator is designed to carry, in kilograms. This is a design capacity, not what's in there at any given moment.
Standard commercial elevators handle 1000-1600 kg, which translates to roughly 13-21 people at 75 kg each. Freight elevators go higher. Residential elevators are often lighter, around 450-630 kg for small installations.
This isn't the same as the actual load factor in operation. Energy modeling uses rated load because that's what determines the motor size, even though the elevator rarely operates at full capacity.
Speed
How fast the elevator moves in meters per second. Common ranges:
Residential, low-rise: 1.0-1.5 m/s
Mid-rise commercial: 2.0-2.5 m/s
High-rise: 3.5-5.0 m/s
Express elevators: 8-10+ m/s
If your plans list speed in feet per minute (which happens more often than it should), divide by 196.85 to convert to m/s.
Speed directly affects power calculation because faster movement means more work done per unit time. A 1.0 m/s elevator uses half the peak power of a 2.0 m/s elevator with otherwise identical specs.
Counterweight (Traction Only)
For buildings over 4 stories, you can specify the counterweight mass or leave it blank.
Most real traction elevators use a counterweight equal to the car weight plus 50% of rated load. This is the sweet spot where the motor does minimal work when the car is half-loaded (the most common operating condition). But ASHRAE's baseline methodology uses car weight plus 40% of rated load.
If you're modeling a baseline, leave this blank and let the calculator use the ASHRAE default. If you're modeling a proposed design with better counterweight balance, enter the actual value to get credit for the efficiency improvement.
The counterweight matters because it reduces the net load the motor has to lift. With perfect counterweighting, the motor only works to move the difference between actual load and counterweight mass. Without a counterweight (hydraulic elevators), the motor lifts the full weight of car plus passengers every trip.
How the Calculation Works
ASHRAE uses a two-step process. The calculator follows this exactly.
Step 1: Calculate Intermediate Power
This determines the mechanical power needed to lift the net load at the specified speed. The 0.00981 factor converts force (measured in kg × m/s) to kilowatts, accounting for gravitational acceleration.
Mechanical efficiency accounts for losses in the sheave system (pulleys), cables, bearings, and guide rails. ASHRAE specifies 58% for hydraulic systems (lots of friction in the hydraulic ram) and 64% for traction systems (more efficient cable-driven mechanism).
Step 2: Account for Motor Efficiency
The motor isn't perfectly efficient at converting electrical power to mechanical work. Motor efficiency comes from lookup tables in the ASHRAE standard. The calculator finds the next motor size larger than your calculated intermediate kW and uses that efficiency percentage.
This is intentional. You don't get credit for a perfectly sized motor in baseline modeling. ASHRAE assumes you size up to the next standard motor, which is how actual installations work. Motors come in discrete sizes, not custom-made to perfectly match every application.
Motor efficiency increases with size (larger motors are generally more efficient) but the relationship isn't linear, which is why the tables exist instead of a simple formula.
Reading the Results
The calculator shows each step so you can verify the logic or explain it to a reviewer:
Motor Type: Hydraulic or Traction, based on building height
Counterweight Used: Either what you specified or the ASHRAE default calculation
Mechanical Efficiency: 58% for hydraulic, 64% for traction
Intermediate kW: Result of step 1 (mechanical power required)
Motor Efficiency: Percentage from the lookup table based on intermediate kW
Peak Motor Power (Pm): Your final answer in kW
This last number goes into your energy model as the maximum electrical draw during peak operation. It's not average consumption throughout the day (which is much lower due to standby periods, partial loads, and regenerative braking in modern systems).
For multiple elevators, you also get total building power, elevator count, average per unit, and estimated annual energy. The annual estimate uses a 60% diversity factor (only 60% of elevators at peak simultaneously), 12 hours per day operation, and 250 working days per year. This is rough. Actual consumption depends heavily on usage patterns.
Building Templates
Four templates cover common configurations:
Residential Low-Rise: 3 floors, 1000 kg load, 1.0 m/s
Typical apartment building elevator
Hydraulic system
Lower speed for comfort and cost
Office Building: 12 floors, 1600 kg load, 2.5 m/s
Standard commercial passenger elevator
Traction system
Higher speed for efficiency
Hospital: 8 floors, 2000 kg load, 1.5 m/s
Service elevator sized for bed transport
Traction system
Moderate speed for patient comfort
Freight/Service: 6 floors, 2500 kg load, 1.0 m/s
Heavy-duty cargo elevator
Traction system
Slower speed, prioritizes capacity over speed
Templates fill all fields with industry-standard values. They're starting points, not gospel. Adjust as needed for your specific building.
Import and Export
Export saves your current work as JSON. Click Export, get a timestamped file with all inputs and results. The file includes:
Current mode (single, multiple, comparison)
All input values
Calculated results
Timestamp
Share this file with colleagues, attach to submittals, or keep for your records.
Import loads a previously exported JSON file. Click Import, select file, calculator automatically switches to the correct mode and populates all fields. Results recalculate immediately.
This workflow works for:
Documentation: Export calculations for code compliance submittals
Collaboration: Share configurations across team members
Version control: Save iterations as you refine designs
Templates: Create standard configurations for similar building types
ASHRAE Reference Tables
The calculator implements three tables from ASHRAE 90.1 Appendix G. These are in the Full Guide tab if you need to reference the exact values being used.
Table G3.9.1 lists motor efficiencies for traction elevators from 0.8 kW (82.5% efficient) up to 149.2 kW (95.0% efficient). 19 discrete sizes.
Table G3.9.2 specifies baseline motor selection: hydraulic for buildings with 4 or fewer stories, traction for buildings with more than 4 stories. Also lists mechanical efficiencies and counterweight requirements.
Table G3.9.3 lists motor efficiencies for hydraulic elevators from 7.5 kW (72% efficient) up to 75 kW (80% efficient). 5 discrete sizes, all less efficient than equivalent traction motors.
The calculator uses these tables automatically. You don't need to look anything up manually.
Common Scenarios
Scenario 1: Simple Office Tower
10-story building, one elevator bank with three identical passenger elevators.
Switch to Multiple Elevators mode
Click Add
Click "Office Building" template
Change "Number of Units" to 3
Name it "Passenger Bank"
Save
Calculate Total Power
Result: Peak power for all three elevators, suitable for electrical system sizing. Annual energy estimate for utility analysis.
Scenario 2: Mixed-Use Building
Retail ground floor, offices above. Different elevator requirements.
Multiple Elevators mode
Add passenger elevator using Office template (12 floors, serves floors 2-12)
Add service elevator using Freight template (12 floors, serves all floors)
Add retail elevator using Residential template (2 floors, ground to basement)
Calculate
Result: Differentiated elevator types with appropriate power requirements for each use.
Scenario 3: Compliance Documentation
Need to show proposed design beats ASHRAE baseline.
Comparison mode
Baseline side: Office template values (what code requires)
Proposed side: Same general specs but lighter car weight (composite materials) and optimized counterweight (car + 50% load instead of 40%)
Compare Performance
Result: Percentage energy savings demonstrating code compliance and supporting narrative for improved design.
Limitations
This calculator implements ASHRAE 90.1 Appendix G baseline methodology. That methodology has specific assumptions baked in. What it is:
A tool for energy code compliance modeling
Suitable for baseline versus proposed comparisons
Appropriate for preliminary energy analysis
What it isn't:
A substitute for elevator engineering
Suitable for detailed operational energy analysis
Going to account for regenerative drives, variable speed controls, or other advanced features
Applicable outside ASHRAE modeling frameworks
ASHRAE baseline models use less efficient elevators than you'll actually install. This is intentional. The baseline represents minimally compliant, older equipment. Your actual building gets credit for improvements during the comparison. Whether this methodology makes sense is a longer conversation than anyone wants to have about elevator modeling, but it's the standard, so here we are.
If your building has unusual elevator configurations (double-deck cars, sky lobbies, destination dispatch systems), the calculator still works for basic power estimation but won't capture the operational complexity. You're on your own for the nuances.
Keyboard Shortcuts
Tab
Navigate between input fields
Enter
Calculate (when focused on input)
Escape
Close modal dialogs
Last updated
Was this helpful?