1 hp=745.7 W

Using the formula W = hp × 745.7, 1 hp converts to 745.7 W. Energy and power have accumulated many units across different disciplines, each defined in the context of a specific field. The SI unit for energy is the joule (J), but practical contexts use kilowatt-hours (kWh) for electricity, calories or kilocalories (kcal) for nutrition, British Thermal Units (BTU) for heating and air conditioning, and electron-volts (eV) for atomic and particle physics. The formula accounts for the precise numerical relationship between these historically distinct measurement traditions.

Electricity consumption on your utility bill is measured in kilowatt-hours (kWh), where 1 kWh = 3,600,000 joules. The "calories" on food packaging are actually kilocalories (1 kcal = 4,184 J) — a naming convention that persists from 19th-century nutritional science. BTU, widely used in HVAC systems and gas appliances in the US, equals about 1,055 joules. Horsepower (hp) measures power (energy per unit time) and equals approximately 746 watts; a 200-hp engine delivers 200 × 746 = 149,200 watts = 149.2 kW. The diversity of energy and power units can make cross-field comparisons confusing, but the conversion factors connecting them are all precisely defined.

Energy conversion comes up when comparing the efficiency of appliances with different energy ratings, estimating electricity costs for heating or cooling systems, interpreting nutritional information on food labels, calculating fuel economy, or working in engineering contexts that require communicating energy values across disciplines. Knowing that 1 hp = 745.7 W helps bridge these domains. Quick reference: 1 kcal (food calorie) ≈ 4,184 J; 1 kWh = 3,600,000 J = 3,412 BTU; 1 BTU ≈ 1,055 J; 1 horsepower = 746 W = 2,545 BTU/hr.