Definition
In an alternating current (AC) electrical system, real power is the portion of the total power that does actual work — producing heat, light, or mechanical motion. It is measured in watts and equals voltage times current times the cosine of the phase angle between them (P = E × I × cos θ). Real power is distinguished from reactive power, which oscillates between source and load without performing useful work, and from apparent power, which is the simple product of voltage and current without regard to phase.
Plain English
The part of the electrical power in an AC system that actually does something useful — like running a motor or heating a wire. The rest of the power sloshes back and forth without getting any work done.
Context Anchor
Seen in aircraft electrical-system discussions, especially when comparing electrical load to what an alternator, generator, or inverter can supply.
Derivation
Called 'real' because it is the power that produces real, measurable work, as opposed to reactive power, which is exchanged between components but never converted into useful output.
Why Pilots Care
Knowing real power lets pilots and technicians calculate true electrical loads and avoid overloading aircraft systems.
Grounding Statement
If you plug a heater into an AC outlet, almost all the power flowing in becomes heat — that useful, work-doing portion is the real power.
Intuition Check
“Real” does not mean “genuine instead of fake” here. It means the portion of electrical power that is actually used to do work, as opposed to power that only appears in the AC circuit calculation.
Example Sentence 1
The generator's real power output dropped when the phase angle between voltage and current increased under load.
Example Sentence 2
Mechanics measure real power to confirm the electrical system meets the aircraft's actual operating demands.