Electrical reference chart
Motor Efficiency Chart
Use this worksheet after the calculator result to record shaft output, input power, losses, load profile, annual kWh, operating cost, and simple payback for an efficiency comparison.
Quick reference table
A motor efficiency chart is a calculator worksheet for turning an efficiency result into an energy and maintenance planning record. Efficiency is output power divided by input power, while project value depends on load profile, operating hours, energy rate, downtime, and replacement cost.
Efficiency result worksheet
| Result item | Record from calculator | Decision note |
|---|---|---|
| Shaft output | Output kW or HP | Confirm the load basis is the same in both cases |
| Input power | Measured or estimated kW | Identify current motor and proposed motor cases |
| Losses | Loss kW or percent | Shows heat and wasted power that may affect enclosure or cooling |
| Annual energy | kWh and cost values | Connects the result to operating hours and energy rate |
| Payback | Simple payback years | Screen against replacement, labor, and downtime cost |
Efficiency comparison inputs
| Input to document | Why the electrician records it | What can change the result |
|---|---|---|
| Load profile | Full load, part load, cycling, or standby duty | Savings can shrink when the motor rarely runs loaded |
| Operating hours | Annual runtime from the calculator | Seasonal process changes and production schedule |
| Measured input | Metered kW, estimated kW, or nameplate assumption | Measurement method and real voltage condition |
| Installed cost | Motor, labor, drive, alignment, and downtime cost | Procurement, outage window, and maintenance scope |
How to use this chart
Record output first
Start with shaft output so input power, losses, and savings are tied to the same mechanical load requirement.
Separate operating cases
Keep existing motor, proposed motor, measured load, and assumed load cases on separate rows before comparing annual energy.
Check payback inputs
Check operating hours, energy rate, installed cost, downtime, and maintenance assumptions before relying on simple payback.
Formula basis
Efficiency = output power / input power x 100%. Losses = input power - output power.
- Output power is the useful shaft output in HP, kW, or watts.
- Input power is the measured or estimated electrical input for the same load condition.
- Losses are the difference between input power and useful output power.
- Annual savings compare input kWh and cost between current and improved cases at the documented operating hours.
Worked examples
Continuous process motor
A motor running most of the year can turn a small input-kW reduction into meaningful kWh savings, so the worksheet keeps load profile, operating hours, and energy rate beside the calculator result.
Standby pump with low runtime
A high-efficiency replacement may show little payback when annual hours are low, so the chart records duty, maintenance value, and downtime notes instead of judging by efficiency alone.
Related calculators
Related charts
Motor Power HP kW Chart
Use a motor power HP kW chart to document horsepower, mechanical output, electrical input, kVA, kVAR, power factor, efficiency, and current context after the calculator result.
kWh Cost Chart
Estimate energy-charge cost from kWh and rate, then separate simple usage cost from demand charges, time-of-use periods, and fixed bill items.
Energy and kWh Conversion Chart
Convert watts, Wh, and kWh: 1,200 W for 3 hours is 3.6 kWh before rate, billing period, duty cycle, or cost checks.
Frequently asked questions
These answers explain how to use the chart without turning a quick reference into a final design decision.