Formula Used
Single phase apparent power: S = V × I ÷ 1000
Single phase real power: P = V × I × PF ÷ 1000
Three phase apparent power: S = √3 × V × I ÷ 1000
Three phase real power: P = √3 × V × I × PF ÷ 1000
Reactive power: Q = √(S² − P²)
Phase angle: θ = cos⁻¹(PF)
Energy: kWh = kW × hours × load factor
Estimated cost: Cost = kWh × energy rate
Power factor correction: kVAR = kW × (tan current angle − tan target angle)
How To Use This Calculator
Select single phase or three phase first. Enter voltage and current when both are known. Use line voltage for three phase systems. Add power factor as a decimal, such as 0.85. If you prefer, leave power factor empty and enter a phase angle. The tool will estimate power factor from that angle.
You can also enter known kW or kVA. When kW is entered, the calculator estimates current and apparent power. When kVA is entered, it estimates real power and current. Add operating hours, load factor, and energy rate to estimate kWh and cost. Enter a target power factor to review correction needs.
Practical AC Power Planning
AC power calculation helps electricians, students, facility teams, and equipment buyers understand how much useful power a circuit can deliver. It also shows how much apparent power the supply must carry. That difference matters because poor power factor raises current, cable heating, transformer loading, and voltage drop. A clear calculator reduces mistakes before a motor, heater, panel, UPS, or generator is selected.
Why Power Factor Matters
In alternating current systems, voltage and current may not peak together. Resistive loads stay close to unity power factor. Motors, compressors, welders, and transformers usually lag because they need magnetic fields. The real power value in kilowatts performs work. The reactive value in kilovars supports fields. The apparent value in kilovolt amps represents total supply burden. Knowing all three gives a better view of the installation.
Single Phase And Three Phase Use
Single phase calculation is common for homes, small offices, and light equipment. Three phase calculation is common for industrial motors, pumps, chillers, data rooms, and commercial panels. The three phase formula uses the square root of three when line voltage and line current are used. This tool keeps that multiplier visible so users can compare both systems without changing the basic workflow.
Energy And Cost Review
Instant power is only part of the decision. Energy cost depends on hours, load factor, and the utility rate. A machine may have a high nameplate rating but run lightly most of the day. Load factor helps model that duty cycle. The estimated cost can support budgeting, audits, and efficiency reviews. It also helps compare old equipment with newer replacements.
Correction And Sizing Notes
The target power factor field estimates required correction kilovars. This value is useful when reviewing capacitor banks. It is only an engineering estimate. Final designs should consider harmonics, switching steps, resonance, standards, protection, and manufacturer data. Always verify voltage, frequency, conductor limits, breaker ratings, temperature, and local codes before purchase or installation.
Better Records
Use the export buttons to save calculations. CSV works well for spreadsheets. PDF gives a simple report for project folders, maintenance notes, or client records. Keep assumptions with every result. Shared records also make later troubleshooting easier for every technician during future service visits.
FAQs
What is AC power?
AC power is electrical power in an alternating current circuit. It changes direction periodically and is used in homes, offices, factories, motors, and power systems.
What is real power?
Real power is the useful power that performs work. It is measured in kilowatts. Motors, heaters, lights, and appliances convert it into motion, heat, or light.
What is apparent power?
Apparent power is the total supply burden. It combines real and reactive power. It is measured in kilovolt amps and helps size generators, transformers, and UPS systems.
What is reactive power?
Reactive power supports magnetic and electric fields in AC equipment. It does not perform direct work, but it affects current, voltage drop, and power factor.
Why does power factor matter?
Low power factor increases current for the same useful power. This can raise losses, heating, cable size, transformer loading, and demand charges in some systems.
Can this calculator handle three phase loads?
Yes. Select three phase and enter line voltage with line current. The calculator applies the square root of three multiplier for balanced three phase systems.
What does target power factor mean?
Target power factor is the desired corrected value. The calculator estimates the kilovars needed to move from the current factor toward that target.
Is the capacitor estimate final?
No. It is only a planning estimate. Final capacitor selection should consider harmonics, switching method, protection, duty, standards, and qualified engineering review.