PowerConvert™ Fast Electrical Power Calculators
kVAR Calculator
Find the reactive power (kVAR) a load draws from its real power and power factor. kVAR is the third side of the power triangle, used when sizing power-factor-correction capacitors.
When to use it
When a site runs a lot of motors, pumps, or chillers, the reactive power they draw pulls the power factor down and forces the supply to carry more kVA than the real work needs. This converter gives the reactive power in kVAR from the real load and its power factor, which is the starting point for sizing a power-factor-correction capacitor bank. It earns its keep on longer hire jobs where a poor power factor is costing capacity.
How it is calculated
kVAR = kW x tan(arccos(PF)), which is kW x the square root of (1 - PF squared), divided by PF. The apparent power is kVA = kW / PF.
100 kW at power factor 0.8: kVAR = 100 x sqrt(1 - 0.64) / 0.8 = 75 kVAR, and kVA = 125.
Common conversions
| Real power (kW) | Reactive power (kVAR) |
|---|---|
| 10 kW | 7.5 kVAR |
| 25 kW | 18.8 kVAR |
| 50 kW | 37.5 kVAR |
| 100 kW | 75.0 kVAR |
| 200 kW | 150.0 kVAR |
| 500 kW | 375.0 kVAR |
Frequently asked questions
How do you calculate kVAR from kW?
Multiply the kW by tan(arccos(power factor)): kVAR = kW x sqrt(1 - PF squared) / PF. For example, 100 kW at 0.8 power factor is 75 kVAR.
What is kVAR used for?
kVAR is reactive power. It sizes power-factor-correction capacitor banks: adding capacitive kVAR offsets the inductive kVAR of motors and transformers, raising the power factor and lowering the kVA the supply must carry.
How are kW, kVA and kVAR related?
They form the power triangle: kVA squared = kW squared + kVAR squared. Real power (kW) and reactive power (kVAR) combine into apparent power (kVA), with the power factor equal to kW / kVA.
How much capacitive kVAR do I need to correct the power factor?
Work out the reactive power at the present power factor and again at the target, then the capacitor bank supplies the difference. This converter gives the present kVAR, which is the first figure in that calculation.
Does correcting power factor reduce the generator size I need?
It reduces the kVA the supply has to carry for the same real work, which can free up capacity on a hire set. The real power in kW does not change, but the apparent power in kVA falls as the power factor rises.