Convert Horsepower to Milliwatts

Power is the rate at which energy is transferred or converted. The SI unit is the watt (W), equal to one joule per second, named for James Watt and the steam-engine improvements that made 18th-century industry possible. Watt also coined horsepower around 1782 to market his engines to brewers familiar with draught horses; he fixed 1 mechanical horsepower at 550 foot-pounds-force per second, which computes to 745.69987158227022 W exactly. Continental Europe later adopted a slightly different metric horsepower (PS, ch, cv) equal to 75 kgf·m/s or 735.49875 W, which is why the same engine often reads a few units higher in horsepower than in PS on identical spec sheets. HVAC work lives in BTU per hour: one ton of refrigeration equals 12,000 BTU/h, or about 3.517 kW. Data centres and utilities step up through kilowatts, megawatts, and gigawatts. Kilocalories per hour appear in heating and metabolism contexts. Our converter uses exact defining relationships so motor ratings, cooling loads, and photovoltaic yields convert consistently.