Power is the rate of energy use. Watts measure electrical power, horsepower measures engine output, and BTU/h rates HVAC equipment.
The Watt
1 W = 1 J/s. Named after James Watt. 1 kW = 1,000 W. A light bulb uses 60 W; a microwave uses 800–1,200 W.
Horsepower
1 mechanical hp = 745.7 W. A car engine produces 100–300 hp. Metric horsepower (PS) = 735.5 W, slightly different.
Quick Conversions
- 1 hp = 745.7 W = 0.746 kW
- 1 kW = 1.341 hp
- 1 kW = 3,412 BTU/h
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Frequently Asked Questions
How many watts are in a horsepower?
1 mechanical hp = 745.7 W. Metric horsepower (PS) = 735.5 W.
How do I convert kW to BTU/h?
Multiply kW by 3,412. A 2 kW heater = 6,824 BTU/h.