Power Factor Correction Calculator

Assumes a lagging sinusoidal load and a kVA-based demand tariff.

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1 Inputs

Minimum: 0.1

Minimum: 0.1 · Maximum: 1

Minimum: 0.1 · Maximum: 1

Minimum: 0

2 Results

Capacitor size needed
94.7 kVAR
kVA before
256.4 kVA
kVA after
210.5 kVA
Demand reduction
45.9 kVA (17.9%)
Annual saving
$8,259
Qc = P × [tan(acos PF₁) − tan(acos PF₂)]
Assumes a lagging sinusoidal load and a kVA-based demand tariff. The calculated reactive requirement is not a capacitor specification. Harmonics, switching, resonance and light-load behaviour require a site-specific electrical design.

Worked example

Example values are illustrative. Replace them with your measured data.

InputValue
Real power (load)200 kW
Present power factor0.78
Target power factor0.95
Demand charge15 $/kVA/mo

Capacitor size needed: 94.7 kVAR

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About this calculator

How it works

Required capacitor size (kVAR) = kW × (tan(arccos PF₁) − tan(arccos PF₂)), where PF₁ is the present power factor and PF₂ the target. Apparent power is kW ÷ PF before and after correction. The kVA reduction × demand charge × 12 gives the estimated annual saving.

Worked example (illustrative inputs)

200 kW load, power factor raised from 0.78 to 0.95, demand charge $15 per kVA per month. Capacitors needed ≈ 94.7 kVAR. kVA falls from 256.4 to 210.5, a cut of 45.9 kVA (17.9%). Estimated saving ≈ $8,259 a year.

How to read the result

The kVA reduction frees transformer and cable capacity and cuts I²R losses. The money saving applies only where your utility bills on kVA or penalises low power factor. Correcting much beyond about 0.95–0.98 rarely pays and can cause over-correction or resonance at light load.

When to use it

Use it to size a capacitor bank from a load's real power and measured power factor, and to check whether the tariff makes correction worthwhile.

À propos de ce calculateur

Traduction (brouillon) — à relire.

Fonctionnement

Puissance de condensateurs requise (kVAR) = kW × (tan(arccos FP₁) − tan(arccos FP₂)), où FP₁ est le facteur de puissance actuel et FP₂ la cible. La puissance apparente vaut kW ÷ FP avant et après correction. La baisse de kVA × prime de puissance × 12 donne l'économie annuelle estimée.

Exemple chiffré (valeurs d'illustration)

Charge de 200 kW, facteur de puissance porté de 0,78 à 0,95, prime de 15 $ par kVA et par mois. Condensateurs ≈ 94,7 kVAR. La puissance apparente passe de 256,4 à 210,5 kVA, soit 45,9 kVA de moins (17,9 %). Économie estimée ≈ 8 259 $/an.

Lire le résultat

La baisse de kVA libère de la capacité sur le transformateur et les câbles, et réduit les pertes Joule. L'économie financière ne vaut que si le fournisseur facture en kVA ou pénalise un faible facteur de puissance. Corriger nettement au-delà de 0,95–0,98 est rarement rentable et peut causer surcompensation ou résonance à faible charge.

Quand l'utiliser

À utiliser pour dimensionner une batterie de condensateurs à partir de la puissance active et du facteur de puissance mesuré, et vérifier si le tarif rend la correction intéressante.

حول هذه الحاسبة

ترجمة (مسودة) — للمراجعة.

طريقة الحساب

حجم المكثفات المطلوب (كيلو فار) = كيلوواط × (tan(arccos PF₁) − tan(arccos PF₂))، حيث PF₁ معامل القدرة الحالي وPF₂ المستهدف. القدرة الظاهرية = كيلوواط ÷ معامل القدرة قبل التصحيح وبعده. انخفاض الكيلو فولت أمبير × رسم الطلب × 12 يعطي الوفر السنوي التقديري.

مثال محسوب (قيم توضيحية)

حمل 200 كيلوواط، رفع معامل القدرة من 0.78 إلى 0.95، رسم طلب 15 دولاراً لكل كيلو فولت أمبير شهرياً. المكثفات ≈ 94.7 كيلو فار. تنخفض القدرة الظاهرية من 256.4 إلى 210.5 كيلو فولت أمبير، بانخفاض 45.9 (17.9%). الوفر التقديري ≈ 8,259 دولاراً سنوياً.

قراءة النتيجة

انخفاض القدرة الظاهرية يحرر سعة المحول والكابلات ويقلل الفقد الحراري. والوفر المالي لا يتحقق إلا إذا كانت الشركة الموردة تحاسب على الكيلو فولت أمبير أو تفرض غرامة على انخفاض معامل القدرة. التصحيح إلى ما بعد 0.95–0.98 تقريباً نادراً ما يكون مجدياً وقد يسبب تصحيحاً زائداً أو رنيناً عند الحمل الخفيف.

متى تستخدمه

استخدمها لتحديد حجم بنك المكثفات من القدرة الفعلية ومعامل القدرة المقاس، والتحقق مما إذا كانت التعرفة تجعل التصحيح مجدياً.

In one line

Assumes a lagging sinusoidal load and a kVA-based demand tariff. The calculated reactive requirement is not a capacitor specification. Harmonics, switching, resonance and light-load behaviour require a site-specific electrical design.

Worked example

EXAMPLE

Illustrative values (the calculator defaults), not data from a real site.

Inputs
Real power (load)200 kW
Present power factor0.78
Target power factor0.95
Demand charge15 $/kVA/mo
Results
Capacitor size needed94.7 kVAR
kVA before256.4 kVA
kVA after210.5 kVA
Demand reduction45.9 kVA (17.9%)
Annual saving$8,259

Frequently asked questions

Why correct power factor?

Low power factor means the utility delivers more apparent power (kVA) than the real power (kW) you use. That can trigger demand or kVA penalties, loads up transformers and cables, and increases losses. Capacitors supply the reactive power locally so the supply only carries real power.

What power factor should I target?

Most plants aim for 0.95–0.98. Going to unity is rarely worth it and can cause over-correction (leading PF) and resonance at light load. Automatic, stepped capacitor banks track the load and avoid over-correction.

How do I find my present power factor?

Your utility bill often states it directly, or you can read it from a power meter or quality analyzer at your main switchboard, or calculate it as kW ÷ kVA from simultaneous readings of both. A low-power-factor penalty line item on your bill is a strong signal correction is worth investigating.

Does this apply to a single motor or a whole facility?

The formula works at any scale — enter the real power of whatever you're correcting, whether that's one large motor or your facility's total billed demand. Facility-wide correction at the main switchboard is more common and administratively simpler, though very large motors are sometimes corrected locally as well.

What's the risk of over-correcting power factor?

Pushing past unity creates a leading power factor, which some utilities also penalise, and at light load can cause voltage rise or resonance with system inductance that damages equipment. Automatic capacitor banks with multiple switched steps avoid this by only engaging enough capacitance to match the current load.

Are there other benefits besides the demand-charge saving shown here?

Yes — improving power factor also reduces I²R losses in cables and transformers, frees up capacity for other loads, and can reduce voltage drop, none of which are quantified in this calculator's dollar figure. Even where your utility doesn't directly bill on kVA, these secondary benefits can still justify correction.

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