Power Factor Calculator
Power factor is the ratio between the power actually doing useful work and the total power the supply has to provide — a number below 1 means some capacity is being 'wasted' on reactive load, even though it's not literally lost as heat.
Inputs
Result
0.8
Reactive power 6 kVAR
How the power factor calculator works
Power factor = real power ÷ apparent power.
Reactive power = √(apparent² − real²), the component that oscillates back and forth without doing net useful work.
Worked example: 8 kW real, 10 kVA apparent
- Power factor = 8 ÷ 10 = 0.8.
- Reactive power = √(10² − 8²) = √(100−64) = √36 = 6 kVAR.
Common mistakes to avoid
Assuming a low power factor means wasted energy on the bill
Reactive power isn't converted to heat or lost as waste — but a poor power factor still means the supply and wiring need to be sized for more current than the useful work alone requires, and many commercial tariffs penalise it directly.
Treating power factor as always improvable to exactly 1
A power factor of exactly 1 means purely resistive load with no reactive component at all — for most real motors and electronic loads, some reactive component is inherent, though it can be corrected closer to 1 with capacitor banks.
Frequently asked questions
Why do industrial electricity bills sometimes include a power-factor penalty?
A poor power factor forces the utility's generation and distribution equipment to handle more current for the same useful power delivered, so some tariffs charge extra to encourage correction.
What causes a low power factor in the first place?
Inductive loads like motors and transformers are the most common cause — they draw reactive current in addition to the real current doing useful work.
How is power factor corrected in practice?
Capacitor banks are added to the circuit to offset the inductive reactive power, bringing the overall power factor closer to 1 without changing the useful work being done.
Can power factor be a value other than between 0 and 1?
No — by definition it's real power divided by apparent power, and apparent power is always at least as large as real power, keeping the ratio between 0 and 1.
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