Wattages

Wattage is the amount of electrical power a device uses or can deliver, measured in watts (W). The watt is the SI unit of power, defined as one joule per second. In common usage, wattage describes how much energy per unit time a device requires to operate, or how much it converts from electrical energy into light, heat, or motion.

Power in electrical circuits can be categorized as real (active) power, apparent power, and reactive power. Real power, measured in watts, represents usable energy. Apparent power, measured in volt-amperes (VA), combines current and voltage without accounting for phase angle. Reactive power, measured in volt-amps reactive (VAR), is associated with energy storage in inductive or capacitive elements. The relation is P = V × I × PF, where PF is the power factor (0–1). In a DC circuit, PF = 1, so P = V × I.

Energy consumption over time is measured in watt-hours or kilowatt-hours. A device rated at P watts consumes P watts as long as it operates; energy used in kilowatt-hours equals (P in kW) × (time in hours).

Devices carry wattage ratings on labels; for lamps, "60W" or "12W LED" indicates real power draw. Designers use wattage to estimate heat, battery life, and electrical load. Large appliances may be rated in kilowatts (kW).

Hardware safety: Higher wattage draws more current for a given voltage (I = P/V). This influences circuit sizing, breaker selection, and wiring. Efficiency and power factor affect actual energy use; higher efficiency reduces waste heat, and a higher power factor reduces apparent power demand.

Origin: The watt is named after James Watt, an eighteenth-century inventor, and is part of the International System of Units (SI).