Three-Phase Power & Cost Estimator
Estimate three-phase real power, apparent power, reactive power, and daily, monthly, and yearly energy cost from voltage, current, and power factor — with service capacity PASS/FAIL checks.
Load Details
A
PF
hrs
$/kWh
A
Live Results
Real Power
22.45kW
Apparent Power
24.94kVA
Reactive Power
10.87kVAR
Daily kWh
179.57
Monthly kWh
5,387.21
Yearly kWh
65,544.42
Daily Cost
$26.94
Monthly Cost
$808.08
Yearly Cost
$9,831.66
Service Capacity Check
PASS30.00 A load vs 60 A service
Input Summary
Voltage480 V
Current30.00 A
Power Factor0.90
Hours Per Day8.00 hrs
Cost Per kWh$0.15
Selected Service Amps60 A
Three-phase power calculations follow standard electrical engineering formulas. Always verify final design with local electrical code.
How to Use This Three-Phase Calculator
- Select system voltage. Choose the three-phase line-to-line voltage for your installation — 208 V for commercial wye systems, 240 V for delta or high-leg configurations, or 480 V for industrial and large commercial feeders. Voltage directly affects apparent power (kVA) and real power (kW) calculations.
- Enter load current. Input the measured or calculated line current in amperes from the motor nameplate, panel schedule, or clamp meter reading. Current represents the load drawn on each phase and is the primary driver of kVA and kW output.
- Set power factor. Enter the load power factor as a decimal between 0 and 1. Motors and inductive equipment typically run between 0.75 and 0.95 PF. Lower power factor increases reactive power (kVAR) and may trigger utility demand charges — use nameplate data when available.
- Enter operating hours and energy rate. Input daily run hours and your utility cost per kilowatt-hour ($/kWh) to estimate daily, monthly, and yearly energy consumption and operating cost. Monthly estimates use 30 days; yearly estimates use 365 days.
- Review power output, cost, and service capacity. Compare kVA, kW, and kVAR results against transformer and feeder ratings. Optionally enter selected service amperage to run a PASS/FAIL check — PASS means load current is within the selected service capacity. Review low power factor and high kVA warnings before finalizing design.
Formulas & Example
Three-phase power calculations convert line voltage and current into apparent, real, and reactive power, then project energy consumption and cost based on operating hours and utility rates.
Apparent Power (kVA) = (Voltage × Current × √3) ÷ 1000
Real Power (kW) = kVA × Power Factor
Reactive Power (kVAR) = kVA × √(1 − PF²)
Daily Energy (kWh) = kW × Hours Per Day
Monthly Energy (kWh) = Daily kWh × 30
Yearly Energy (kWh) = Daily kWh × 365
Daily Cost = Daily kWh × Cost Per kWh
Monthly Cost = Monthly kWh × Cost Per kWh
Yearly Cost = Yearly kWh × Cost Per kWh
Service PASS/FAIL = Current ≤ Selected Service AmpsWorked Example
A 480 V three-phase load drawing 30 A at 0.90 power factor:
Voltage = 480 V
Current = 30 A
Power Factor = 0.90
kVA = (480 × 30 × 1.732) ÷ 1000 ≈ 24.9 kVA
kW = 24.9 × 0.90 ≈ 22.4 kW
kVAR = 24.9 × √(1 − 0.90²) ≈ 10.9 kVARPair this tool with the Motor FLA Calculator, Transformer Sizing Calculator, Load Calculation Tool, Voltage Drop Calculator, and EV Charger Circuit & Load Calculator for complete three-phase system planning.
Frequently Asked Questions
What is three-phase power?â–¾
Three-phase power is an AC electrical distribution method that delivers power through three alternating current waveforms offset by 120 degrees. It is the standard for commercial and industrial facilities because it provides smoother motor torque, higher power density, and more efficient transmission than single-phase. Three-phase apparent power is calculated as kVA = (V × I × √3) ÷ 1000, where V is line-to-line voltage and I is line current.
What is the difference between kW, kVA, and kVAR?â–¾
kW (kilowatts) is real power — the actual work performed by the load, such as turning a motor shaft or producing heat. kVA (kilovolt-amperes) is apparent power — the total power the electrical system must deliver, including both real and reactive components. kVAR (kilovolt-amperes reactive) is reactive power — the energy stored and returned by inductive loads like motors and transformers. The relationship is: kW = kVA × power factor, and kVAR = kVA × √(1 − PF²).
What affects energy cost?â–¾
Energy cost is determined by real power consumption (kW), operating hours, and your utility rate ($/kWh). Reactive power (kVAR) does not directly appear on simple energy bills but low power factor can trigger demand charges on commercial and industrial accounts. Running equipment longer, at higher current, or at lower power factor all increase total electrical cost. Seasonal rate tiers, time-of-use pricing, and demand ratchets can further affect monthly and yearly totals beyond this calculator's flat-rate estimate.
What is power factor?â–¾
Power factor is the ratio of real power (kW) to apparent power (kVA), expressed as a decimal from 0 to 1. A PF of 0.90 means 90% of the current delivers useful work; the remaining 10% is reactive current that still loads conductors and transformers. Inductive loads like motors, compressors, and fluorescent ballasts reduce power factor. Utilities may penalize accounts below 0.85–0.90 PF with demand surcharges — power factor correction capacitors can improve PF and reduce charges.
How do utilities bill three-phase loads?â–¾
Commercial and industrial three-phase accounts are typically billed on energy (kWh), demand (kW or kVA peak), and sometimes power factor penalties. Energy charges multiply kWh consumed by the rate per kWh. Demand charges bill the highest average kW or kVA over a 15- or 30-minute interval during the billing period. Low power factor can increase apparent demand, raising the demand charge even when real power consumption is moderate. Residential accounts are usually billed on kWh only without demand or PF penalties.
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