When to Use This Calculator
Use this calculator when you need to move between real power, reactive power, apparent power, power factor, and phase angle for a sinusoidal AC load or balanced power-system estimate.
Select Known Values
Formula Summary
MVA2 = MW2 + MVAR2
PF = MW ÷ MVA
φ = cos-1(PF)
Lagging reactive power is displayed as positive MVAR; leading reactive power is displayed as negative MVAR.
Practical Examples
Substation load check
An 80 MW load with 60 MVAR lagging has 100 MVA apparent power, 0.80 power factor, and a 36.87° phase angle.
Transformer loading estimate
A 25 MVA load at 0.90 PF carries 22.5 MW and about 10.9 MVAR. That MVA value is the loading quantity to compare with transformer apparent-power rating.
Assumptions
This tool uses the fundamental-frequency power triangle. Distorted waveforms can require true power factor and harmonic quantities beyond displacement power factor.
MVAR sign conventions vary among utilities and software. Confirm the convention used by the system study or operating display.
Common Mistakes
- Treating kW and kVA as interchangeable when power factor is below 1.0.
- Mixing leading and lagging MVAR sign conventions between tools.
- Using displacement power factor when harmonic distortion makes true power factor different.
- Comparing MW to equipment kVA or MVA ratings without converting apparent power.
Reference Notes
The power triangle is a standard sinusoidal AC power relationship used in circuit analysis and power-system studies. For billing, metering, protection, or interconnection work, use the utility, meter, study software, or applicable standard's sign and measurement conventions.