# Motor Energy Cost Calculator

> Motor Energy Cost: Input kW = rated kW × load ÷ efficiency. Methodology stated, your own inputs only.

Page: https://freecalculator.tech/tools/motor-energy-cost-calculator
Last reviewed: 2026-10-20

## Formula

Input kW = rated kW × load ÷ efficiency. Cost = input kW × hours × price.

- Methodology: electrical input = shaft output ÷ efficiency, with energy = power × time (OpenStax College Physics, power).
- Efficiency changes with load — use the manufacturer's figure for your load point.
- No price or efficiency is assumed.
- Input kW = rated kW × load ÷ efficiency. Cost = input kW × hours × price.
- Inputs used: Currency (symbol only, never converted), Motor rated output, Average load (share of rated output), Motor efficiency at that load (nameplate or manufacturer), Running hours in the period, Your energy price per kWh (from your bill or a saved rate).

## Inputs

- Currency (symbol only, never converted)
- Motor rated output
- Average load (share of rated output)
- Motor efficiency at that load (nameplate or manufacturer)
- Running hours in the period
- Your energy price per kWh (from your bill or a saved rate)

## Worked example: A fan motor

15 kW motor at 75% load, 92% efficient, 4,000 hours at $0.12.
1. 15 × 0.75 ÷ 0.92 = 12.228 kW.
2. 12.228 × 4,000 = 48,913 kWh.
3. 48,913 × 0.12 = $5,869.57.

## Common questions

### Why isn't an electricity or fuel price filled in?

Prices differ by country, supplier, tariff and time of use, so there is no universal figure. Enter the rate from your bill or contract, or pick a dated saved rate if one is listed on the page.

### Where do I find efficiency?

On the nameplate or the manufacturer's data sheet, ideally at the load you actually run. Check the formula, example, and limitations on this page before using the result for a real energy decision.

### Does this include the drive?

No. If a variable-speed drive is fitted, divide by its efficiency as well, or measure input power directly.

### How do I use the Motor Energy Cost Calculator?

Enter the required values for Currency (symbol only, never converted), Motor rated output, Average load (share of rated output), Motor efficiency at that load (nameplate or manufacturer), Running hours in the period, and the other fields shown. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Motor Energy Cost Calculator use?

Input kW = rated kW × load ÷ efficiency. Cost = input kW × hours × price. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

### Can the Motor Energy Cost Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- Constant average load; for varying duty, split into periods.
- Power factor and drive losses are not included.
- Results are estimates built only from the figures you enter. No electricity, fuel or gas price, equipment efficiency or benchmark is built in — tariffs vary by supplier, region and time, and equipment data must come from the manufacturer. Designs and installations must be checked by a qualified professional.
- The result depends on the values you enter for this motor energy cost calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- OpenStax — https://openstax.org/books/college-physics-2e/pages/7-7-power

## Cite this page

- APA: Free Calculator. (2026, October 20). Motor Energy Cost Calculator. https://freecalculator.tech/tools/motor-energy-cost-calculator
- MLA: "Motor Energy Cost Calculator." Free Calculator, 20 Oct. 2026, https://freecalculator.tech/tools/motor-energy-cost-calculator.
- Link: Motor Energy Cost Calculator — Free Calculator, https://freecalculator.tech/tools/motor-energy-cost-calculator