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Reactive Power Converter
Convert VAR, kVAR and MVAR, and see why utilities bill for power that does no work.
Pour a beer and you get liquid and foam. The liquid is what you actually drink; the foam takes up space in the glass and does nothing for you. Electrical power works the same way — real power is the liquid, reactive power is the foam, and an AC circuit has to carry both.
Power that flows without doing work
In an AC circuit with motors, transformers or fluorescent ballasts, the current and voltage drift out of step with each other. Some of the power genuinely does work — turning a shaft, producing light, heating an element — and is measured in watts. The rest sloshes back and forth between the source and the magnetic field of the equipment, never converting into anything useful, and is measured in VAR: volt-amperes reactive.
Reactive power is not wasted energy in the sense of being burned off as heat. It genuinely returns to the source each cycle. But the wires, transformers and generators still have to be sized to carry it, which is precisely why it costs someone money even though it does no work.
The three numbers on a power triangle
- Real power (W, kW) — the power that does actual work — what your electricity meter mostly charges for.
- Reactive power (VAR, kVAR) — the power that oscillates between source and load without being consumed, caused by inductive or capacitive loads.
- Apparent power (VA, kVA) — the combination of the two, and the figure that determines how thick your cables and transformers actually need to be.
- Power factor — real power divided by apparent power. A power factor of 1.0 means no reactive power at all; large industrial motors often sit closer to 0.7–0.85.
Converting between VAR units
| From | To VAR | To kVAR | To MVAR |
|---|---|---|---|
| 1 VAR | 1 | 0.001 | 0.000001 |
| 1 kVAR | 1,000 | 1 | 0.001 |
| 1 MVAR | 1,000,000 | 1,000 | 1 |
Why industrial customers get billed for it
A factory full of induction motors can pull a lot of reactive power even while its actual energy use, in kWh, looks moderate. The utility still has to build and maintain infrastructure sized for the higher apparent power, so many commercial and industrial tariffs include a power-factor penalty or a separate kVAR charge once the power factor drops below a threshold, often around 0.9 or 0.95. Installing capacitor banks to offset the reactive draw is a standard, well-understood fix, and it is why you will see banks of capacitors sitting next to large motors in factories.
Reactive power questions
What does VAR actually stand for?
Volt-ampere reactive. It has the same dimensional units as watts (volts multiplied by amps) but is kept as a separate unit precisely because it represents power that does not do useful work, unlike watts.
Why does reactive power matter if it is not consumed?
Because the generators, transformers and cables in the system still have to be sized to carry the total current, real and reactive combined. A low power factor means more current for the same useful output, and more current means thicker cables, bigger transformers and higher losses.
How do I convert kVAR to kW?
You cannot directly, because they measure different things. You need the power factor: kW equals kVA multiplied by the power factor, and kVAR relates to both through the power triangle (kVA squared equals kW squared plus kVAR squared).
What is a good power factor?
Above 0.95 is generally considered good for an industrial site, with 1.0 being the theoretical ideal of no reactive power at all. Utilities commonly start applying penalty charges once a site falls below 0.9.
How do capacitor banks help with reactive power?
Most industrial reactive power is inductive, caused by motors and transformers. Capacitors produce reactive power of the opposite sign, so adding capacitor banks locally cancels out much of the inductive reactive power before it has to travel back through the utility’s wires.
