Power Unit Converter (W, kW, hp, CV, BTU/h)
Convert power between watts, kilowatts, megawatts, mechanical horsepower (hp), metric horsepower (CV/PS), BTU per hour, kcal/h and tons of refrigeration — e.g. hp to kW and kW to hp.
How it works
value in target unit = value × (watts per source unit) ÷ (watts per target unit) · 1 hp = 745.69987 W · 1 CV (PS) = 735.49875 W · 1 BTU/h = 0.29307107 W · 1 TR = 12,000 BTU/h
Every unit is converted through the watt, the SI unit of power (one joule per second). Mechanical horsepower is 550 foot-pounds-force per second = 745.7 W and is used for US and UK engines; metric horsepower (CV in Spanish, PS in German) is 75 kilogram-force meters per second = 735.5 W and appears on many European and Latin American car spec sheets. Air conditioners are rated in BTU per hour or tons of refrigeration (1 TR = 12,000 BTU/h = 3.517 kW).
Worked example
100 hp × 745.69987 W = 74,569.99 W; ÷ 1,000 = 74.57 kW. The same engine is 101.39 CV (metric horsepower).
Sources: NIST SP 811, Appendix B — Conversion factors · BIPM — The International System of Units (SI Brochure)
Frequently asked questions
How do I convert hp to kW?
Multiply horsepower by 0.7457: 150 hp × 0.7457 = 111.9 kW. To go from kW to hp, multiply by 1.341: 100 kW = 134.1 hp.
What is the difference between hp and CV (PS)?
A mechanical horsepower (hp) is 745.7 W; a metric horsepower (CV, PS, ch) is 735.5 W, about 1.4% smaller. So 100 hp = 101.4 CV, and 100 CV = 98.6 hp.
How many BTU/h is 1 kW?
1 kW = 3,412.14 BTU/h. A 12,000 BTU/h air conditioner (one ton of refrigeration) delivers 3.52 kW of cooling.
Is power the same as energy?
No. Power is the rate of energy use. A 2 kW heater running for 3 hours uses 6 kWh of energy; use the energy unit converter for kWh, joules and calories.
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