Convert between power units
A watt is the SI unit of power (1 joule/second). Horsepower is an older unit: 1 hp = 745.7 watts. A typical car engine is 100-300 hp (75-224 kW). Home appliances are usually rated in watts.
Power (watts) = Voltage × Current. Energy (kWh) = Power × Time. A 1000W appliance running 5 hours uses 5 kWh. Check your electricity rate to calculate cost. 1 kW running 1 hour = 1 kWh.
kW is real power (actual work done). kVA is apparent power (voltage × current). The ratio (power factor) is typically 0.8-0.95 for most loads. Utility companies may charge for both, especially for businesses.
Mechanical hp = 745.7W, metric hp = 735.5W, boiler hp = 9810W. Different definitions evolved in different countries/industries. Always clarify which horsepower is meant, especially for engines and motors.
A resting human produces about 80-100 watts of heat. During intense exercise, output can reach 300-400 watts briefly. Elite cyclists sustain 400W+. The human body is roughly 25% efficient at converting food to work.
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