How many joules is 1 mechanical horsepower-hour?

1 mechanical horsepower-hour equals exactly 2,684,519.537 joules (approximately 2.685 MJ). This is derived from 1 mechanical hp = 745.69987 W, multiplied by 3,600 seconds per hour.

What is the difference between horsepower-hours and horsepower-seconds?

Horsepower-hours (hp·h) represent the energy produced by one horsepower running for one full hour. Horsepower-seconds (hp·s) represent just one second of output. 1 hp·h = 3,600 hp·s, so they differ by a factor of 3,600.

Why are there three horsepower variants?

Mechanical (imperial/SAE) horsepower is defined as 550 ft-lbf/s = 745.69987 W and is standard in North American automotive ratings. Electrical horsepower is exactly 746 W, used for electric motors. Metric horsepower (PS/CV) is 75 kgf·m/s = 735.499 W, common in European automotive specifications.

How does this differ from a horsepower to kilowatts converter?

Horsepower (hp) is a unit of POWER (energy per unit time). This tool converts horsepower × time, which is ENERGY. You must supply a duration (hours or seconds) to obtain an energy result in joules.

How many BTU is 1 mechanical horsepower-hour?

1 mechanical horsepower-hour equals approximately 2,544.43 BTU. This is a commonly used equivalence in HVAC and heat engine analysis.

Can I convert horsepower-seconds to kWh?

Yes. Select the horsepower-seconds mode and the calculator will show the kWh equivalent. For reference, 1 mechanical hp·s = 0.000207 kWh (about 745.7 watt-seconds = 0.000207 kWh).

Horsepower to Joules Calculator

Name: Horsepower to Joules Calculator
Availability: InStock
Author: Nham Vu

Enter horsepower-hours or horsepower-seconds and get the equivalent energy in joules, kWh, BTU, kcal, and foot-pounds for mechanical, metric, or electrical horsepower.

Energy Input

Time Base

Horsepower Type

Horsepower-Hours (hp·h)

Power Constants (watts)

1 hp (mechanical) = 745.69987 W
1 hp (electrical) = 746.00000 W
1 hp (metric, PS) = 735.49875 W

Time Multiplier

hp·h: × 3,600 s (= 1 hour)
hp·s: × 1 s

Results Click a row to copy

Enter a value to see results

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Summary

Enter horsepower-hours or horsepower-seconds and get the equivalent energy in joules, kWh, BTU, kcal, and foot-pounds for mechanical, metric, or electrical horsepower.

How it works

Enter the energy quantity as a number in the input field.
Select the time base: horsepower-hours (hp·h) for large energy amounts, or horsepower-seconds (hp·s) for smaller values.
Choose the horsepower variant: mechanical (SAE), electrical, or metric (PS/CV).
The tool multiplies the watt value of your chosen HP type by the number of seconds implied (3600 s/h or 1 s), giving energy in joules.
Five equivalent energy values update instantly: joules, kilowatt-hours, BTU, kilocalories, and foot-pounds.
Click any result row to copy the value to your clipboard.

Use cases

Calculate the energy content of a fuel or battery rated in horsepower-hours.
Convert engine work output from hp·h to joules for thermodynamic analysis.
Compare generator energy production listed in hp-hours against kWh billing.
Size capacitor banks or flywheel storage from horsepower-second ratings.
Academic engineering problems converting between imperial and SI energy units.
Verify pump or compressor energy data on mixed-unit specification sheets.
Convert heating system output from BTU to joules for SI-based design.
Cross-check kcal equivalents for mechanical work in sports science research.

Frequently Asked Questions

Last updated: 2026-06-14 · Reviewed by Nham Vu