What is gigawatt?

A gigawatt is a unit of power equal to one billion watts. It is used to express the total power output of national electricity grids, large power stations, and national energy policy targets.

Real-world uses

Gigawatts describe the generating capacity of entire national grids, large hydroelectric dams (Three Gorges Dam: ~22.5 GW), and the total installed solar or wind capacity of countries. Global electricity demand is often expressed in terawatts (1,000 GW). Energy policy discussions use GW to compare national ambitions.

History

Gigawatts entered common use in discussions of national and continental electricity systems during the 20th century. As installed generation capacity in large countries reached the gigawatt scale, this unit became standard for energy policy, grid planning, and international energy statistics.

Common mistakes

Confusing GW (power) with GWh (energy). A 22 GW dam running at full capacity for one hour generates 22 GWh of energy. Also, the pop-culture reference "1.21 gigawatts" from Back to the Future is frequently cited but would equal about 1,210 MW—a large power plant.

What is milliwatt?

A milliwatt is a unit of power equal to one thousandth of a watt. It is used in low-power electronics, wireless communication systems, laser specifications, and medical device power ratings.

Real-world uses

Milliwatts measure the power of laser pointers (Class 1: <1 mW; Class 3B: up to 500 mW), Bluetooth radios (typically 1–100 mW), Wi-Fi transmitters, and fibre optic signals. They are used in optical communications, consumer electronics, and medical laser specifications.

History

Milliwatts became relevant as the miniaturisation era brought small electrical and optical devices into widespread use from the mid-20th century. Consumer electronics, telecommunications, and biomedical equipment all required power specifications at this sub-watt scale.

Common mistakes

Confusing milliwatts (mW) with microwatts (µW)—1 mW = 1,000 µW. Also, assuming all laser pointers operate at the same power level; safety regulations classify lasers by output power in mW, and even small increases can be hazardous to the eyes.

When is this conversion used?

Converting gigawatt to milliwatt is useful in the power domain when comparing values across different measurement standards or applying formulas that require a specific unit.

Worked examples

1 gigawatt = 1.000000e+12 milliwatt

1 milliwatt = 0.001 watt

How to convert gigawatt to milliwatt

To convert gigawatt to milliwatt, multiply the value by 1.000000e+12.

To convert milliwatt back to gigawatt, multiply by 1.000000e-12.

Measurement standards

The watt is the SI derived unit of power, defined as one joule per second (kg·m²/s³). Horsepower remains in widespread informal use, particularly in the automotive industry, but has no single universal definition across regions.

Did you know?

The human body at rest produces about 80 watts of power — roughly enough to keep an incandescent light bulb glowing. During intense exercise, a trained cyclist can sustain over 400 watts, and elite sprinters briefly exceed 2,000 watts.

Quick reference: gigawatt to milliwatt

Common values

Available Power units

• watt conversions
• kilowatt conversions
• horsepower (mechanical) conversions
• megawatt conversions
• gigawatt conversions
• milliwatt conversions
• microwatt conversions
• BTU per hour conversions
• kilocalorie per hour conversions
• ton of refrigeration conversions

More gigawatt conversions

• Convert gigawatt to watt
• Convert gigawatt to kilowatt
• Convert gigawatt to horsepower (mechanical)
• Convert gigawatt to megawatt
• Convert gigawatt to milliwatt
• Convert gigawatt to microwatt
• Convert gigawatt to BTU per hour
• Convert gigawatt to kilocalorie per hour
• Convert gigawatt to ton of refrigeration

Assumption: horsepower values use mechanical horsepower.