Definition
The unit of electrical power, equal to one joule of energy used per second. In a direct current circuit, watts are calculated by multiplying voltage by current (W = V × A). One watt represents the rate at which work is done or energy is transferred.
Plain English
A measure of how much electrical work is being done at any given moment. The bigger the watt number, the more power something is using or producing.
Context Anchor
Seen in aircraft electrical system discussions, equipment ratings, generator or alternator output, lights, heaters, and maintenance manuals.
Derivation
Named after James Watt, the Scottish engineer who improved the steam engine in the 1700s. The unit was adopted in his honour because his work made the measurement of mechanical and electrical power practical.
Why Pilots Care
Aircraft electrical systems have limits. Knowing the wattage of installed equipment helps confirm the generator or alternator can carry the load without overloading the system or tripping a circuit breaker.
Analogy
Watts are like the rate of water flowing from a hose. Volts are the push, amperes are the amount of flow, and watts describe how much useful power is being delivered.
Intuition Check
Do not treat watts as the same thing as volts or amperes. Volts describe electrical push, amperes describe electrical flow, and watts describe the power being used or supplied.
Example Sentence 1
The pilot checked the equipment list and confirmed that the total wattage of the avionics did not exceed the alternator's output.
Example Sentence 2
The technician checked that the alternator could supply enough watts for all the radios and instruments.