Power Factor Correction Calculator
A 100 kW plant at 0.78 power factor is billed as if it drew 109 kW — the 85% rule adds about ₱3,100 a month at a ₱350/kW demand charge. A 50 kVAr capacitor bank takes the same plant to 0.95 and the penalty to zero.
Enter your load, your power factor from the bill, and your demand charge. The calculator sizes the capacitor bank (Qc = P(tanφ₁ − tanφ₂), per IEEE Std 141), checks you against the Philippine Distribution Code 85% minimum, and shows the monthly peso saving.
Your Plant & Tariff
Correction Results
| Property | Before | After Correction |
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The Formulas
Capacitor bank size (IEEE Std 141, §8 — power factor improvement):
Apparent power and current (three-phase):
85% rule billing adjustment (common Philippine utility scheme — confirm against your own tariff):
Method & Sources
Every constant in this tool has a source. Nothing is approximated.
- 85% minimum power factor — Philippine Distribution Code, §3.2.2: end-users shall maintain a power factor of not less than 85% lagging at the connection point. Your distribution utility's approved tariff sets the exact billing adjustment used when you fall below it.
- Capacitor sizing formula Qc = P(tanφ₁ − tanφ₂) — IEEE Std 141 (Recommended Practice for Electric Power Distribution for Industrial Plants), the "Red Book".
- Standard bank sizes — the calculator rounds up to the next standard low-voltage bank step (5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200, 250, 300, 400, 500 kVAr). Banks are built to IEC 60831-1/-2.
- What we deliberately leave out — harmonic study, detuned reactor selection, and switching steps. Those need a site survey; a calculator that pretended otherwise would be guessing.
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Frequently Asked Questions
What is the minimum power factor required in the Philippines?
The Philippine Distribution Code (§3.2.2) requires end-users to maintain a power factor of at least 85% lagging at the connection point. Below 85%, your distribution utility may adjust your billed demand — a common scheme multiplies it by 0.85 ÷ your actual power factor. The exact mechanism is in your utility's approved tariff, so check your own bill.
How do I size a power factor correction capacitor bank?
Required reactive power: Qc = P(tanφ₁ − tanφ₂). Example: a 100 kW load at 0.78 power factor corrected to 0.95 needs 100 × (0.802 − 0.329) = 47.4 kVAr — so you fit the next standard size, 50 kVAr. This is the IEEE Std 141 method, and it is exactly what this calculator does.
How much does low power factor cost me each month?
Under the 85% adjustment scheme, a plant recording 100 kW at 0.78 power factor is billed as if it drew 109 kW. At ₱350/kW that is about ₱3,140 a month — roughly ₱37,700 a year — for power you never used. If your utility bills demand in kVA, the penalty hides inside a bigger kVA number instead. Either way, it is on your bill every month until corrected.
Will power factor correction reduce my kWh bill?
Mostly no — and you should walk away from anyone who promises otherwise. Capacitors cut demand charges, penalties, cable losses, and transformer loading. Your kWh consumption stays almost the same. If the goal is a smaller kWh bill, the levers are more efficient equipment — heat pumps instead of resistance heating, inverter drives — or making your own power with solar.
What equipment causes low power factor?
Induction motors — compressors, pumps, fans, conveyors — especially running lightly loaded. Welders, old magnetic fluorescent ballasts, and idling transformers add to it. A motor-heavy plant typically sits between 0.70 and 0.85 uncorrected.
What standards apply to capacitor banks?
Low-voltage banks are built to IEC 60831-1/-2 (self-healing shunt capacitors up to 1,000 V); sizing practice follows IEEE Std 141. One catch worth knowing: if your site runs many variable speed drives, harmonics can damage plain capacitors — the bank should use detuned reactors. Have harmonics checked before installing.
Not Sure What Your Power Factor Is?
It is printed on your monthly electricity bill. Send us a photo of the bill and our engineers will read it, check the penalty, and tell you plainly whether correction pays.
Send Us Your Bill