Power factor correction (kVAR) calculator
Enter the load in kW, the existing power factor and the target. You get the kVAR to install, a rounded bank size, the kVA released on your transformer and the drop in line current.
Basis
Q = P × (tan φ₁ − tan φ₂).
Reference values for planning and comparison. Confirm against the current standard, the purchaser’s specification and the manufacturer’s datasheet before ordering.
kVAR per kW multiplier
| Existing PF | to 0.90 | to 0.95 | to 0.98 | to 1.00 |
|---|---|---|---|---|
| 0.7 | 0.536 | 0.692 | 0.817 | 1.02 |
| 0.75 | 0.398 | 0.553 | 0.679 | 0.882 |
| 0.8 | 0.266 | 0.421 | 0.547 | 0.75 |
| 0.85 | 0.135 | 0.291 | 0.417 | 0.62 |
| 0.9 | — | 0.156 | 0.281 | 0.484 |
Worked example: 400 kW from 0.75 to 0.95 power factor
- tan φ₁ = 0.882, tan φ₂ = 0.329.
- Q = 400 × (0.882 − 0.329) = 221 kVAR.
- Demand falls from 533 kVA to 421 kVA, releasing 112 kVA of transformer capacity.
How much kVAR is needed to improve power factor from 0.8 to 0.95?
About 0.42 kVAR per kW. For a 500 kW load that is roughly 210 kVAR.
Why does power factor matter for a transformer?
A transformer is rated in kVA. Raising power factor reduces the kVA drawn for the same kW, which frees capacity and cuts current and losses in cables.
Should the bank correct to unity?
Usually not. Targets of 0.95 to 0.99 avoid over-correction at light load. Check the tariff requirement of your utility.