Convert Horsepower-Hours to Kilojoules
Convert Horsepower-Hours (hp·h) to Kilojoules (kJ) instantly and accurately.
Conversion Formula
kJ = hp·h × 2684.519538
About Horsepower-Hours
A horsepower-hour (hp·h) is the energy from one mechanical horsepower (745.6999 W) for one hour - exactly 2,684,519.54 J ≈ 2.685 MJ. James Watt coined the horsepower to compare his steam engines with mine horses; billing in hp·h preceded the kilowatt-hour tariff. The metric horsepower (PS = 75 kgf·m/s = 735.499 W) gives a slightly smaller metric-hp·h = 2,647,795 J, used in European and Japanese engine datasheets. Today the hp·h appears in marine engineering logs, mining energy accounting, and vintage industrial equipment. 1 hp·h = 2.6845 MJ = 0.74570 kWh = 641.19 kcal.
About Kilojoules
A kilojoule (kJ) is exactly 1,000 J and is the standard energy unit for food and physical chemistry. EU, Australian, and NZ food labels are mandatory in kJ: recommended adult intake is ~8,400 kJ/day. Bond dissociation energies: C-H bond 413 kJ/mol; C=C double bond 614 kJ/mol; N≡N triple bond 945 kJ/mol. Specific heat of water: 4.184 kJ/(kg·K). A cyclist riding at 150 W for one hour expends 540 kJ. Charpy and Izod impact toughness tests record results in J and kJ. 1 kJ = 1,000 J = 239.0 cal = 0.94782 BTU = 0.27778 Wh.
Quick Reference Table
| Horsepower-Hours (hp·h) | Kilojoules (kJ) |
|---|---|
| 1 hp·h | 2684.52 kJ |
| 2 hp·h | 5369.04 kJ |
| 5 hp·h | 13422.6 kJ |
| 10 hp·h | 26845.2 kJ |
| 25 hp·h | 67113 kJ |
| 50 hp·h | 134226 kJ |
| 100 hp·h | 268452 kJ |