Units of Power

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Created by: Team Physics - Examples.com, Last Updated: April 25, 2024

Units of Power

Power is a fundamental concept in physics that describes the rate at which work is done or energy is transferred over time. Understanding units of power is essential for gauging the efficiency of machines and energy systems in various contexts, from household appliances to large-scale industrial operations.

What are Units of Power?

Power measures the rate of energy transfer or the rate at which work is done. Various units help quantify power in different contexts, enabling precise calculations for energy management and engineering designs.

Transitioning to larger scales, the kilowatt (kW), which equals 1,000 watts, frequently measures the energy consumption of appliances and entire households, providing a clear picture of energy usage.

SI Unit of Power

watt (W)

The SI (International System of Units) unit of power is the watt (W). Defined as one joule per second, the watt measures the rate at which energy is used or produced. It is a crucial unit for quantifying the energy conversion in electrical appliances, vehicles, and power systems, allowing for precise calculations of energy efficiency and consumption in various scientific, engineering, and everyday contexts.

CGS Unit of Power

erg per second

The CGS (Centimeter-Gram-Second) unit of power is the erg per second. An erg is a small unit of energy in the CGS system, where one erg is defined as the work done by a force of one dyne exerted over a distance of one centimeter. Therefore, one erg per second represents the power involved when one erg of energy is transferred in one second. This unit, though less commonly used today compared to the SI unit of power, the watt, is still relevant in specific scientific fields such as physics and astrophysics for detailed micro-scale energy measurements.

List of Power Units

Metric HorsepowerPS
British Thermal Unit per hourBTU/h
Foot-pound per minuteft-lb/min

Watt (W)

1W = 1J/s

The Watt is the SI unit of power named after James Watt. It measures the rate at which work is done or energy is transferred when one joule is expended in one second. It is universally used in science, engineering, and everyday electrical appliances to quantify power.

Kilowatt (kW)

1kW = 1000W

A kilowatt equals one thousand watts and is commonly used to express the power output of engines and the power usage of appliances. It represents the energy production or consumption at a rate of one thousand joules per second.

Megawatt (MW)

1MW = 1,000,000W

A megawatt is a unit of power typically used to describe the capacity of large power plants or the amount of electricity required by large equipment. It equates to one million watts of power.

Gigawatt (GW)

1GW = 1,000,000,000W

The gigawatt is used in major energy production or consumption contexts, such as national power grids or large data centers, representing one billion watts.

Horsepower (hp)

1 hp ≈ 746W

Horsepower is traditionally used in the automotive industry and mechanical engineering to measure engine power. It originated as a unit to compare the power of steam engines with that of draft horses.

Metric Horsepower (PS)

1 PS = 735.5W

Metric horsepower, or PS (Pferdestärke), is slightly different than the mechanical horsepower and is used primarily in Europe to denote the power output of motor engines.

British Thermal Unit per hour (BTU/h)

1 BTU/h ≈ 0.293W

This unit is often used in heating and air conditioning industries in the United States to measure the power of HVAC systems.

Foot-pound per second (ft-lb/s)

1 ft-lb/s ≈ 1.356W

This unit measures the power in terms of mechanical work done when a force of one pound-force is exerted along one foot in one second. It is used in mechanical engineering and in the U.S. for various applications.

Conversion of Power Units

Conversion of Power Units

Here’s a conversion table for various units of power, formatted to provide clear conversion factors between watts, kilowatts, megawatts, gigawatts, and horsepower:

UnitWatts (W)Kilowatts (kW)Megawatts (MW)Gigawatts (GW)Horsepower (hp)
Watts (W)10.0011E-61E-90.00134102
Kilowatts (kW)100010.0011E-61.34102
Megawatts (MW)1E6100010.0011341.02
Gigawatts (GW)1E91E6100011.34102E6
Horsepower (hp)745.70.74570.00074577.457E-71

Watt to Kilowatt

  • Conversion: 1 kilowatt = 1000 watts.
  • Example: To convert 1500 watts to kilowatts, divide by 1000.
  • 1500 W / 1000 = 1.5 kW

Watt to Megawatt

  • Conversion: 1 megawatt = 1,000,000 watts.
  • Example: To convert 2,000,000 watts to megawatts, divide by 1,000,000.
  • 2000000 W / 1000000 = 2 MW

Watt to Gigawatt

  • Conversion: 1 gigawatt = 1,000,000,000 watts.
  • Example: To convert 3,000,000,000 watts to gigawatts, divide by 1,000,000,000.
  • 3000000000 W / 1000000000 = 3 GW

Kilowatt to Watt

  • Conversion: 1 watt = 0.001 kilowatts.
  • Example: To convert 250 kilowatts to watts, multiply by 1000.
  • 250 kW * 1000 = 250000 W

Kilowatt to Megawatt

  • Conversion: 1 megawatt = 1000 kilowatts.
  • Example: To convert 5 kilowatts to megawatts, divide by 1000.
  • 5 kW / 1000 = 0.005 MW

Kilowatt to Gigawatt

  • Conversion: 1 gigawatt = 1,000,000 kilowatts.
  • Example: To convert 6000 kilowatts to gigawatts, divide by 1,000,000.
  • 6000 kW / 1000000 = 0.006 GW

Megawatt to Watt

  • Conversion: 1 watt = 1E-6 megawatts.
  • Example: To convert 1 megawatt to watts, multiply by 1,000,000.
  • 1 MW * 1000000 = 1000000 W

Megawatt to Kilowatt

  • Conversion: 1 kilowatt = 0.001 megawatts.
  • Example: To convert 2 megawatts to kilowatts, multiply by 1000.
  • 2 MW * 1000 = 2000 kW

Megawatt to Gigawatt

  • Conversion: 1 gigawatt = 1000 megawatts.
  • Example: To convert 3 megawatts to gigawatts, divide by 1000.
  • 3 MW / 1000 = 0.003 GW

Gigawatt to Watt

  • Conversion: 1 watt = 1E-9 gigawatts.
  • Example: To convert 1 gigawatt to watts, multiply by 1,000,000,000.
  • 1 GW * 1000000000 = 1000000000 W

Gigawatt to Kilowatt

  • Conversion: 1 kilowatt = 1E-6 gigawatts.
  • Example: To convert 4 gigawatts to kilowatts, multiply by 1,000,000.
  • 4 GW * 1000000 = 4000000 kW

Gigawatt to Megawatt

  • Conversion: 1 megawatt = 0.001 gigawatts.
  • Example: To convert 5 gigawatts to megawatts, multiply by 1000.
  • 5 GW * 1000 = 5000 MW


What are power units called?

Power units, such as watts, kilowatts, and horsepower, quantify the rate at which energy is transferred or work is performed over time.

What is a measure of power?

Power is measured in terms of energy output per unit of time, typically represented by units like watts, indicating the rapidity of energy conversion.

What is power in energy?

In the context of energy, power describes the speed at which energy is used or generated, essentially reflecting the efficiency and capability of energy systems.

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