Power Factor Calculator

Real power, kW

Apparent power, kVA

Target power factor

Advanced options

Voltage, V

Frequency, Hz

Result

Power factor0.8
VerdictНизкий, стоит компенсировать
Phase angle, °36.87
Reactive power, kVAr6
Correction needed, kVAr3.371
Capacitance, µF74.3

How much current works and how much just circulates

Computes the power factor, the reactive power behind it and the capacitance needed to reach a target figure.

Power factor says what share of the current drawn does useful work. A heater sits at one — all of it becomes heat. An induction motor falls to 0.7, because part of the current goes into building a magnetic field and returns to the supply.

That circulating current produces nothing but still heats cables and loads the transformer. Industrial users are billed for it, and the standard remedy is capacitors that offset the load's inductance.

What this calculator shows

The power factor and the phase angle in degrees
Reactive power and how much of it must be corrected to hit the target
The capacitance in microfarads to do that correction

What to keep in mind

The power triangle uses Pythagoras: apparent squared equals real squared plus reactive squared.
Capacitance is computed for a three-phase connection at the stated frequency; in practice banks are switched in steps.

FAQs

What counts as a good power factor?

Above 0.95 is excellent, 0.85 to 0.95 acceptable. Below 0.85 utilities start penalising industrial customers.

Do I need correction at home?

No. A domestic meter records real energy only, so reactive power costs you nothing. Correction pays off where many motors run.

Why does a motor spoil the power factor?

It has to magnetise its core, and that energy shuttles between supply and winding twice per cycle. It performs no work but does put current in the cables.

Can you over-correct?

Yes, and it is harmful: excess capacitance raises the voltage and creates capacitive reactive power instead. That is why the target is 0.95 rather than one, and why banks are switched in steps.

Worked example

A workshop full of motors

Input: 8 kW real against 10 kVA apparent, target 0.95

Output: Power factor 0.8, correct 3.37 kVAr

Note: After correction apparent power falls from 10 to 8.4 kVA and the current by sixteen percent. Cable and transformer are relieved and the reactive charge disappears.

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Power Factor Calculator

Result

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