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Power Unit Conversion Chart

Quick reference guide for power measurement units

Standard Power Units

Unit	Symbol	SI Equivalent	Description
Watt	W	J/s (joule per second)	SI unit of power
Kilowatt	kW	1,000 W	Common unit for electrical devices
Megawatt	MW	1,000,000 W	Power plant/industrial scale
Horsepower (mechanical)	hp	745.7 W	Traditional power unit
Horsepower (metric)	PS	735.5 W	European standard
BTU per hour	BTU/h	0.2931 W	Heating/cooling applications
Foot-pound per second	ft·lbf/s	1.3558 W	Imperial mechanical power

Electrical Power Units

Unit	Symbol	Definition	Application
Volt-ampere	VA	V × A	Apparent power in AC circuits
Kilovolt-ampere	kVA	1,000 VA	Transformer/equipment rating
Volt-ampere reactive	VAR	V × A × sin(φ)	Reactive power
Watt (real power)	W	V × A × cos(φ)	Actual power consumption
Decibel-milliwatt	dBm	10 × log₁₀(P/1mW)	Communications systems

Power Density Units

Unit	Symbol	SI Equivalent	Application
Watt per square meter	W/m²	W/m²	Irradiance, heat flux
Watt per cubic meter	W/m³	W/m³	Volumetric power density
BTU per hour per square foot	BTU/h·ft²	3.1546 W/m²	HVAC applications
Watt per kilogram	W/kg	W/kg	Specific power (batteries, motors)
Horsepower per cubic inch	hp/in³	45.5 MW/m³	Engine power density

Common Power Unit Conversions

From	To	Conversion Factor	Example
Watts (W)	Horsepower (hp)	Divide by 745.7	1,000 W = 1.341 hp
Horsepower (hp)	Watts (W)	Multiply by 745.7	1 hp = 745.7 W
Kilowatts (kW)	BTU/hour	Multiply by 3,412.14	1 kW = 3,412.14 BTU/h
BTU/hour	Watts (W)	Multiply by 0.2931	1,000 BTU/h = 293.1 W
Metric horsepower (PS)	Watts (W)	Multiply by 735.5	1 PS = 735.5 W
Foot-pound per minute	Watts (W)	Multiply by 0.0226	1,000 ft·lbf/min = 22.6 W
Volt-ampere (VA)	Watts (W)	Multiply by power factor	1,000 VA × 0.8 PF = 800 W
W/m²	BTU/h·ft²	Multiply by 0.3170	100 W/m² = 31.7 BTU/h·ft²

Typical Power Requirements

Device or Application	Typical Power Range	Watts	Horsepower
LED light bulb	5-15 W	5-15 W	0.007-0.020 hp
Laptop computer	45-100 W	45-100 W	0.060-0.134 hp
Refrigerator	100-800 W	100-800 W	0.13-1.07 hp
Microwave oven	700-1,200 W	700-1,200 W	0.94-1.61 hp
Home air conditioner	1-4 kW	1,000-4,000 W	1.34-5.36 hp
Electric vehicle motor	50-200 kW	50,000-200,000 W	67-268 hp
Residential home (average)	1.2 kW (average)	1,200 W	1.61 hp
Small wind turbine	1-10 kW	1,000-10,000 W	1.34-13.4 hp
Industrial motor	5-500 hp	3,728-372,850 W	5-500 hp
Small power plant	1-10 MW	1,000,000-10,000,000 W	1,340-13,400 hp

Key Power Equations

Electrical power: P = V × I (P = power in watts, V = voltage in volts, I = current in amperes)
Three-phase power: P = √3 × V × I × PF (PF = power factor, typically 0.8-0.9)
Mechanical power: P = F × v (F = force in newtons, v = velocity in meters per second)
Rotational power: P = τ × ω (τ = torque in newton-meters, ω = angular velocity in radians per second)
Horsepower to watts: P(W) = P(hp) × 745.7
Kilowatts to BTU/hour: P(BTU/h) = P(kW) × 3,412.14
Power in resistive load: P = I² × R (R = resistance in ohms)
Electrical energy: E(kWh) = P(kW) × t(h)

Practical Examples of Power Conversions

Electric Motor Rating

A 5-horsepower electric motor has an equivalent power of 5 hp × 745.7 W/hp = 3,728.5 watts or 3.73 kilowatts. For nameplate rating, this would typically be rounded to 3.7 kW in metric specifications.

HVAC System Sizing

A 36,000 BTU/h air conditioner has a power rating of 36,000 BTU/h × 0.2931 W/(BTU/h) = 10,552 watts or approximately 10.6 kW. This is equivalent to about 14.1 horsepower.

Solar Panel Output

A 300-watt solar panel under full sun (1,000 W/m²) with 20% efficiency would require 1.5 square meters of surface area. Over 5 hours of peak sunlight, it would generate 300 W × 5 h = 1,500 watt-hours (1.5 kWh) of energy.

Vehicle Engine Comparison

A 150 PS European car engine rating equals 150 PS × 735.5 W/PS = 110,325 watts or 110.3 kW. This is equivalent to approximately 148 hp in mechanical horsepower. Many manufacturers use these units interchangeably despite the small difference.