Three Phase Load Calculator

Analyze balanced loads with fast electrical performance estimates. Check phase current, apparent power, and demand. Size feeders accurately using clear assumptions and instant outputs.

Balanced three-phase electrical load estimation with energy and cost outputs.

Calculator Inputs

Enter the known system values to estimate electrical load, energy use, and operating cost.

Layout adapts to 3 columns on large screens, 2 on smaller screens, and 1 on mobile.
Choose the parameter you already know. The calculator derives the remaining values from it.
Enter the selected known value using its matching unit.
Connection type affects phase voltage and phase current values in the result section.
Use the measured or rated three-phase supply voltage between any two lines.
Typical operating values often range from 0.80 to 0.98 for industrial loads.
Efficiency is used when mechanical output and operating cost estimates are required.
Demand factor scales connected power to the expected maximum demand load.
Load factor helps estimate typical monthly and annual energy use from rated power.
Use your average loaded operating hours for realistic energy and cost estimates.
Monthly operating days determine projected monthly and annual energy totals.
Enter the tariff used for operating cost calculations, excluding taxes if preferred.
Examples include $, €, Rs, or AED. The symbol appears in cost results and exports.
Frequency is displayed in the output summary for documentation and reporting.
Reset

Example Data Table

These sample cases show how the calculator behaves with different known quantities and operating assumptions.

Scenario Known Basis Known Value VLL PF Input kW kVA Line Current Monthly Energy Monthly Cost
Plant fan bank Electrical input power 45.00 kW 400 V 0.92 45.00 kW 48.91 kVA 70.60 A 8,190.00 kWh $ 1,146.60
Process chiller Apparent power 75.00 kVA 480 V 0.88 66.00 kW 75.00 kVA 90.21 A 19,008.00 kWh $ 2,090.88
Compressor line Line current 120.00 A 415 V 0.90 77.63 kW 86.26 kVA 120.00 A 10,091.97 kWh $ 1,614.71

Formula Used

The calculator assumes a balanced three-phase system. Use line-to-line voltage and line current for the main power equations.

Apparent Power (kVA) = sqrt(3) x VLL x IL / 1000 Real Power Input (kW) = Apparent Power x Power Factor Reactive Power (kVAR) = sqrt((kVA^2) - (kW^2)) Line Current (A) = kVA x 1000 / (sqrt(3) x VLL) Electrical Input (kW) = Mechanical Output (kW) / Efficiency Phase Voltage, Wye = VLL / sqrt(3) Phase Current, Delta = IL / sqrt(3) Monthly Energy (kWh) = kW x Load Factor x Hours per Day x Days per Month Monthly Cost = Monthly Energy x Energy Rate Demand Load (kW) = Real Power Input x Demand Factor
Important: Load factor and demand factor should be entered as percentages. The calculator converts them internally into decimal multipliers.

How to Use This Calculator

  1. Select the known basis that matches the data you already have, such as power, apparent power, or line current.
  2. Enter the system line-to-line voltage, connection type, power factor, and efficiency.
  3. Provide demand factor, load factor, operating time, tariff rate, and currency symbol for cost calculations.
  4. Press Calculate Load to show the result above the form under the page header.
  5. Review the summary metrics, input snapshot, and detailed output table.
  6. Use the CSV button for spreadsheets and the PDF button for a printable report.

Load Current Visibility

Three-phase studies usually begin with current because cable heating, breaker sizing, and voltage drop depend on amperes. In a balanced system, line current increases with apparent power and decreases as line-to-line voltage rises. A 45 kW load at 400 V and 0.92 power factor draws about 70.60 A. That number helps engineers compare duty with feeder capacity and protection settings.

Power Triangle Interpretation

The calculator separates apparent power, real power, and reactive power so the power triangle is visible. Real power performs useful work, while reactive power supports magnetic fields. With 45.00 kW at 0.92 power factor, apparent power becomes 48.91 kVA and reactive power is about 19.20 kVAR. These values matter when sizing switchgear, capacitor banks, generators, and transformer loading margins in systems.

Effect of Connection Type

Connection type changes phase quantities even when total three-phase load stays constant. In a wye circuit, phase voltage equals line voltage divided by the square root of three. In delta, phase current equals line current divided by the same factor. Showing both results helps technicians check motor assumptions, relay settings, and instrument transformer ratios before commissioning, troubleshooting, or retrofit work on equipment.

Demand and Operating Profile

Connected load rarely operates at full rating all day. Demand factor estimates expected demand, while load factor represents average utilization. If a 45 kW load uses an 85 percent demand factor, expected demand becomes 38.25 kW. With a 70 percent load factor, 10 hours per day, and 26 days monthly, projected energy reaches 8,190 kWh. That supports budgeting, tariff review, and schedule comparisons.

Efficiency and Delivered Output

Efficiency becomes important when the known quantity is mechanical output or when asset performance is reviewed. A machine delivering 42.75 kW at 95 percent efficiency requires 45.00 kW electrical input. The difference appears as losses and affects operating cost. Reviewing efficiency with power factor helps teams distinguish process losses from reactive loading issues in motors, pumps, compressors, and driven machinery.

Cost-Based Decision Support

Electrical calculations become more useful when converted into money. At an energy rate of 0.14 per kWh, monthly cost for 8,190 kWh equals 1,146.60, while annual cost reaches 13,759.20. Presenting cost beside current and power values helps justify power factor correction, staged operation, control upgrades, or equipment replacement. The calculator supports technical review and financial planning from one balanced-load model.

FAQs

Why can apparent power exceed real power?

Apparent power includes both working power and reactive power. Inductive loads such as motors require magnetic support current, so kVA is usually higher than kW whenever power factor is below one.

Does the calculator work for unbalanced loads?

It is intended for balanced three-phase systems. If the phase currents or phase voltages differ materially, calculate each phase separately or use measured phase data for a more accurate study.

How should I choose demand factor?

Use historical demand records, design diversity assumptions, or operating studies. Demand factor reflects the expected maximum simultaneous loading relative to connected power, not the average monthly operating level.

Why is efficiency needed for some cases?

Efficiency links electrical input to delivered mechanical output. When you know shaft power, the calculator uses efficiency to estimate the electrical power required from the three-phase supply.

Which voltage should I enter?

Enter line-to-line voltage, measured between any two phases. Common examples include 400 V, 415 V, 440 V, and 480 V systems used in industrial and commercial installations.

Can I use the cost figures for budgeting?

Yes, for preliminary budgeting. However, final energy bills may also include demand charges, fuel adjustments, fixed service fees, taxes, and penalties or incentives related to power factor.