Convert Watts to Horsepower

The Watt (symbol: W) is a unit of power. The SI unit of power (ISO 80000-5 §5-19), defined as exactly one joule per second (1 W = 1 J/s = 1 kg·m²/s³ = 1 V·A in electrical systems). Named after Scottish mechanical engineer James Watt (1736-1819), whose late-18th-century improvements to the Newcomen atmospheric steam engine (separate condenser, sun-and-planet gear) launched the Industrial Revolution and made power-unit standardization economically necessary. The watt is the universal electrical and mechanical power unit across scientific publication, engineering, consumer electronics, and energy markets. Reference values: a typical 9 W LED bulb produces ~800 lumens (equivalent to a 60 W incandescent at 14 lm/W luminous efficacy); audio equipment output power (a hi-fi home amplifier 50-200 W per channel; a concert PA system 5,000-50,000 W); a modern crystalline-silicon residential solar PV module ~350-450 W peak per panel under STC; a household refrigerator continuous load ~150 W average; a high-end gaming PC at full load ~700 W; a Tesla Model S Plaid peak motor output ~760 kW (1,020 hp); the world's electricity-generating capacity ~8 TW (8 × 10¹² W).

It belongs to the metric measurement system.

Watts are commonly used in electrical systems, automotive performance, and HVAC sizing.

The Horsepower (symbol: hp) is a unit of power. An imperial unit of power equal to approximately 745.7 watts (mechanical horsepower per NIST SP 811: 1 hp = 33,000 ft·lbf/min exactly = 550 ft·lbf/s = 745.69987158227022 W). Originally defined by James Watt in the 1780s by measuring how much coal a typical pit-pony could lift from a Cornish coal mine, then scaled up to match draft-horse-team output for marketing his steam engines. Horsepower remains the dominant US power unit for: passenger-car engines (a typical sedan 150-300 hp; full-size pickup 350-450 hp; Tesla Model S Plaid 1,020 hp; Bugatti Chiron Super Sport 1,578 hp), outboard motors (Mercury Verado 600 hp), agricultural tractors (John Deere 8R 410 hp), riding lawn equipment, residential HVAC blower motors, RV gen-sets, marine inboards, and industrial electric motors per NEMA MG-1 ratings. **Important**: 'Metric horsepower' or PS / CV (Pferdestärke / Cheval Vapeur) is slightly different at exactly 735.49875 W per 1985 EU directive — a detail that matters when comparing US-spec vs European-spec engine ratings (German auto-magazine '500 PS' is ~493 US hp). Convert hp to kW by multiplying by 0.7457; to BTU/hr by multiplying by 2,544.

It belongs to the imperial measurement system.

Horsepower are commonly used in electrical systems, automotive performance, and HVAC sizing.