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Electrical Calculator (Watt, Capacitor, 3-Phase)

Calculate Watt-Volt-Ampere, capacitor (reactance/time constant), kWh consumption, and 3-phase power for industrial use.

MATHEMATICS

Electrical calculator for power, capacitance, energy usage, and 3-phase systems — for both household and industrial use.

Four tabs: Watt-Volt-Ampere (P = V × I), capacitor (reactance Xc, time constant τ, stored energy), kWh usage with utility tariff brackets, and 3-phase power (real / apparent / reactive).

Disclaimer: Utility tariffs change. For actual electrical installation work, consult a certified electrician.

Electrical Calculator

Calculate power, capacitor properties, energy consumption (kWh), and 3-phase power for home and industrial electrical applications.

Power law: P = V x I. Enter any two values to calculate the third. Use power factor (cos phi) for AC loads.

Calculations are estimates. Actual readings depend on appliance condition, voltage stability, and PLN tariff updates. Consult a licensed electrician for installation.

Calculator information

How to use this calculator

  1. Select the type of calculation: power (Watt-Volt-Ampere), capacitor, kWh, or 3-phase system.
  2. For power: enter 2 of 3 values (V, I, P) and power factor (cos phi) for AC.
  3. For capacitor: enter capacitance (uF), frequency (60 Hz US standard), and voltage.
  4. For kWh: enter the appliance power (Watts), daily usage duration, and your utility rate per kWh (US average ~$0.16/kWh per EIA).
  5. For 3-phase: enter line voltage (208V or 480V US standard), current, and cos phi for apparent/real/reactive power.
  6. Click Calculate for the result and recommendations (breaker size, monthly cost, power factor correlation).

Ohm's Law, AC Power, and 3-Phase System

P = V * I * cos phi ; Xc = 1/(2*pi*f*C) ; kWh = P(W) * t(h) / 1000 ; P_3ph = sqrt(3) * V_LL * I_L * cos phi
  • P = active power (Watts); V = voltage (Volts); I = current (Amperes)
  • cos phi = power factor (0.85-0.95 for inductive loads)
  • Xc = capacitive reactance (ohms); f = frequency (Hz); C = capacitance (Farads)
  • V_LL = line-to-line voltage (208V or 480V in the US); I_L = line current
  • Apparent power S (VA) = V * I ; Reactive Q (VAR) = V * I * sin phi

US standard: 120V/60Hz for single-phase residential, 208V or 480V/60Hz for three-phase commercial/industrial. Utilities may bill kVAh or apply demand charges for industrial customers.

Worked example: Window AC 1 ton (~1,200 W) used 8 hours/day, US average rate $0.16/kWh

Given:
  • AC power ~ 1,200 W
  • Voltage 120 V, cos phi 0.85
  • Duration: 8 hours/day, 30 days
  • Electric rate: $0.16/kWh (EIA US average, 2025)
Steps:
  1. Current I = P / (V * cos phi) = 1200 / (120 * 0.85) = 11.76 A
  2. Daily kWh = 1200 * 8 / 1000 = 9.6 kWh
  3. Monthly kWh = 9.6 * 30 = 288 kWh
  4. Monthly cost = 288 * $0.16 = $46.08
  5. Breaker size >= 11.76 * 1.25 = 14.7 A -> select 15 A breaker (NEC 210.19)

Result: Consumption 288 kWh/month, cost $46.08. Use a 15 A breaker for protection.

Frequently asked questions

What is the difference between Watts, Volts, and Amperes?
Volt (V) = voltage, the potential difference that drives current. Ampere (A) = current, the number of electrons per second. Watt (W) = power, the rate of energy used = V * A for DC, or V * A * cos phi for AC. Water analogy: Volt = pressure, Ampere = flow rate, Watt = total power. US residential standard is 120V.
What is power factor (cos phi) and why does it matter?
Power factor is the ratio of active power (W) to apparent power (VA). PF of 1.0 is ideal (purely resistive). Inductive loads (motors, AC, refrigerators) have PF of 0.7-0.85, meaning VA exceeds W. US utilities often charge industrial customers penalties if PF < 0.90 because it wastes grid capacity. The fix is installing a capacitor bank for PF correction.
How do I calculate my monthly electric bill?
Total kWh = sum(appliance wattage * hours used) / 1000. Multiply by your utility rate per kWh. US average is ~$0.16/kWh (EIA 2025), but it varies widely: Hawaii ~$0.40/kWh, Washington ~$0.10/kWh. Add monthly customer/service charges ($10-$30 typical) and any demand charges or taxes. Check your utility's tariff sheet for tiered or time-of-use pricing.
What is a 3-phase system and when is it needed?
A 3-phase (3-ph) system delivers continuous power for large motors and industrial loads >5 kVA. Three AC waveforms offset by 120 degrees deliver power equal to sqrt(3) * V_LL * I_L * cos phi. Advantages: smooth motor torque, copper savings (smaller wire per kW), and balanced loading. Required for water pumps, compressors, and central air handlers in commercial buildings.
How do I select a safe electrical wire size?
Calculate current I = P/V (or P/(V*cos phi) for AC), multiply by a safety factor of 1.25 (NEC 210.19). Choose wire per NEC Table 310.16 ampacity ratings: 14 AWG = 15 A, 12 AWG = 20 A, 10 AWG = 30 A, 8 AWG = 40 A, 6 AWG = 55 A (75 degC copper). For wire runs longer than 100 ft, upsize one gauge to keep voltage drop below 3%.

Last updated: May 11, 2026

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