How the Power Converter Works

A power converter changes a power value between common units such as the watt (W), kilowatt (kW), horsepower (hp) and BTU per hour (BTU/h). Power is the rate at which energy is used or produced, defined as energy per unit time. The SI unit is the watt, equal to one joule per second.

Because different industries measure power differently, conversions are common. Engines are rated in horsepower, electrical devices in watts and kilowatts, and heating or cooling equipment in BTU per hour. The converter expresses each unit in terms of the watt and rescales, letting you compare a car engine, a microwave and an air conditioner on the same footing.

Power Conversion Factors

Every power unit relates to the watt by a fixed factor. Use these standard values:

• 1 kilowatt (kW) = 1,000 W
• 1 horsepower (hp, mechanical) ≈ 745.7 W
• 1 BTU per hour ≈ 0.293071 W
• 1 kilowatt ≈ 1.341 hp
• 1 kilowatt ≈ 3,412.14 BTU/h

For example, to convert a 150 hp engine to kilowatts: 150 × 745.7 = 111,855 W = about 111.9 kW. To convert a 12,000 BTU/h air conditioner to watts: 12,000 × 0.293071 = about 3,517 W, or roughly 3.5 kW. The mechanical horsepower of 745.7 W is the value used in most engine ratings.

Common Power Conversions

This reference table compares the four units against one kilowatt, a convenient anchor for electrical and mechanical power.

Unit	Value (= 1 kW)
Watt (W)	1,000
Kilowatt (kW)	1
Horsepower (hp)	1.341
BTU per hour (BTU/h)	3,412.14

These values show how the units scale. A one-kilowatt heater produces 3,412 BTU/h of heat, while a one-horsepower motor draws about 0.746 kW of mechanical power. The relationship between watts and BTU/h is especially useful when sizing air conditioners and furnaces.

Power Units in Practice

Choosing the right unit depends on the application. Watts and kilowatts are the universal SI measures for electrical appliances, solar panels and power plants. Horsepower remains the traditional unit for car, truck and motor ratings, with one mechanical horsepower equal to about 745.7 watts.

BTU per hour dominates in HVAC, rating the heating and cooling capacity of furnaces and air conditioners. Because all of these trace back to the watt, you can easily compare an electric motor in horsepower to its draw in kilowatts, or convert an air conditioner's BTU/h rating into the equivalent wattage for an energy comparison. The same factors give consistent, accurate results every time.

Types of Horsepower and Common Pitfalls

One detail that trips people up is that horsepower has more than one definition. The mechanical (or imperial) horsepower used here equals about 745.7 watts and is standard for car and engine ratings. The metric horsepower (often written PS or CV) is slightly smaller at about 735.5 watts, and is common in European and Asian vehicle specifications. There is also electrical horsepower, defined as exactly 746 watts for motors. The differences are small but matter for precise engineering.

Another common mix-up is treating power and energy as the same thing. Power (watts) is the rate of energy use, while energy (joules or kilowatt-hours) is the total amount used over time. A 2,000-watt heater running for one hour consumes 2 kilowatt-hours of energy. Keeping this distinction clear prevents errors when comparing appliance ratings to electricity bills.

When converting an air conditioner or furnace rating, watch the units: BTU/h measures the rate of heat transfer, not total heat. To find the equivalent electrical power, multiply BTU/h by 0.293071 to get watts. Because every unit here reduces to the watt, you can always cross-check by converting both figures to watts and comparing them directly, giving you confidence in any motor, heater or appliance comparison.