Methods: Power factor correction
calc.power-factor.correct · Version 0.1.0
Method
Correction in kVAR is kW × (tan(arccos(PF now)) − tan(arccos(PF target))); apparent power is kW ÷ PF; line current is kVA × 1,000 ÷ (√3 × V) for three-phase service. On a tariff that bills demand scaled to a power-factor threshold, billing kW is kW × threshold ÷ PF when PF is lower.
Assumptions
- The power factor entered (or computed from kVAR or kVA) is the one the utility bills on; a bill or the meter shows it.
- Correction is sized for the kW entered, usually the demand-setting load.
Sources
- U.S. Department of Energy, Energy Efficiency and Renewable Energy, "Reducing Power Factor Cost", Motor Challenge fact sheet, Power triangle example: 100 kW and 100 kVAR, corrected to 0.95 with a 67 kVAR capacitor
- Washington State University Energy Program and the Northwest Energy Efficiency Alliance, "Energy Efficiency Factsheet: Reducing Power Factor Cost" (published by Clark Public Utilities), Factsheet, Figure 4: a 100 kW load at 0.70 corrected to 0.95 with a 69 kVAR capacitor
Worked examples
| Example | Independent source | Tolerance | Last result |
|---|---|---|---|
| 500 kW at 0.78, corrected to 0.95 | calc/power-factor-correction spec, scenarios "Correcting 0.78 to 0.95" and "Billing-demand adjustment removed" | ±0.05, ±0.05, ±0.05, ±0.01 | Passed on Oct 31, 2026 |
| DOE example: 100 kW and 100 kVAR, to 0.95 | DOE "Reducing Power Factor Cost": a 67 kVAR capacitor | ±1 | Passed on Oct 31, 2026 |
| WSU and NEEA example: 100 kW at 0.70, to 0.95 | WSU and NEEA factsheet, Figure 4: a 69 kVAR capacitor | ±1 | Passed on Oct 31, 2026 |
Known differences from reference engines
None recorded.
Cite this tool
Power factor correction, version 0.1.0. gridprims. https://gridprims.com/tools/calc/power-factor/correct/