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In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit).
Electric power is the rate of transfer of electrical energy within a circuit.Its SI unit is the watt, the general unit of power, defined as one joule per second.Standard prefixes apply to watts as with other SI units: thousands, millions and billions of watts are called kilowatts, megawatts and gigawatts respectively.
A kilowatt-hour is a unit of energy. Kilowatt per hour would be a rate of change of power flow with time. Work is the amount of energy transferred to a system; power is the rate of delivery of energy. Energy is measured in joules, or watt-seconds. Power is measured in watts, or joules per second. For example, a battery stores energy.
A unit of electrical energy, particularly for utility bills, is the kilowatt-hour (kWh); [3] one kilowatt-hour is equivalent to 3.6 megajoules. Electricity usage is often given in units of kilowatt-hours per year or other periods. [4] This is a measurement of average power consumption, meaning the average rate at which energy is transferred ...
Nameplates on electrical motors show their power output, not the power input (the power delivered at the shaft, not the power consumed to drive the motor). This power output is ordinarily stated in watts or kilowatts. In the United States, the power output is stated in horsepower which, for this purpose, is defined as exactly 746 watts.
The dimension of power is energy divided by time. In the International System of Units (SI), the unit of power is the watt (W), which is equal to one joule per second. Other common and traditional measures are horsepower (hp), comparing to the power of a horse; one mechanical horsepower equals about 745.7 watts.
In the context of domestic PV installations, the kilowatt (symbol kW) is the most common unit for nominal power, for example P peak = 1 kW. Colloquial English sometimes conflates the quantity power and its unit by using the non-standard label watt-peak (symbol W p), possibly prefixed as in kilowatt-peak (kW p), megawatt-peak (MW p), etc.
kilo-(kW) 1–3 × 10 3 W tech: heat output of a domestic electric kettle: 1.1 × 10 3 W tech: power of a microwave oven: 1.366 × 10 3 W astro: power per square meter received from the Sun at the Earth's orbit: 1.5 × 10 3 W tech: legal limit of power output of an amateur radio station in the United States up to 2 × 10 3 W