Power-Factor Correction Calculator
A poor power factor makes KPLC bill you for kVA you never turn into useful work — and on commercial and industrial tariffs, maximum demand is billed at up to KES 1,100 per kVA every month. Enter your active power, existing power factor and target, and this calculator returns the required capacitor-bank rating in kvar, the reduction in current and kVA, the cut in cable and transformer losses, and an approximate saving in shillings with a simple payback estimate.
Not sure of your existing power factor? It is on your KPLC bill — or estimate your demand first with the Electricity Bill Calculator.
Correction summary CALC-08 · REV 2026-07
| Required capacitive power, Qc | – |
|---|---|
| Recommended capacitor bank | – |
| Apparent power, before → after | – |
| kVA reduction released | – |
| Line current, before → after | – |
| Current reduction | – |
| Cable I²R loss reduction | – |
| Demand-charge saving | – |
| Approximate payback | – |
Guidance tool only. Savings assume the billed maximum demand falls in proportion to the corrected power factor at that demand. A real installation must check harmonic content (VFDs, UPS and LED loads may need detuned reactors to avoid resonance), switching transients, step sizing against load variation, and protection — work for a registered engineer.
How this calculator works
- Capacitor demand. The reactive power to be supplied by the bank is Qc = P × (tan φ₁ − tan φ₂), where φ = cos⁻¹(pf). The result is rounded up to a standard bank rating, with a step configuration suggested — fixed banks up to about 30 kvar, automatic multi-step banks above.
- What improves. At the same active power, apparent power falls from P÷pf₁ to P÷pf₂, and line current falls in the same proportion (1 − pf₁/pf₂). Cable and transformer I²R losses fall with the square of that ratio — correcting 0.75 to 0.95 cuts them by about 38%.
- The savings. KPLC CI tariffs bill maximum demand in kVA (KES 1,100/kVA at CI1 down to 200 at CI6), so the released kVA converts directly to a monthly saving, and the bank cost per kvar gives a simple payback — commonly under a year for loads below 0.85.
- Sensible limits. Kenyan supply agreements require at least 0.9; 0.95 is the usual design target. Above about 0.97 the calculator warns about over-correction at light load and harmonic resonance — VFD- or UPS-heavy sites should use detuned reactors.
Assumptions and limits
- Savings assume the billed maximum demand occurs at (or near) the corrected power factor; time-varying loads need an automatic bank sized from a week of logging.
- Harmonic studies, switching transients, protection and step control are outside this tool and essential in the installed design.
Want the survey, the harmonic screening and a guaranteed design? See our consultancy services, or learn the method in a training program.