Electrical Power Calculator Widget

Add a single-phase and DC power calculator to your website. Visitors find real power from voltage and current, or the current an appliance draws from its wattage, with the power factor taken into account for AC loads.

Electrical & Electronics Calculator Runs in your browser Free · no ads

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<iframe src="https://a2z.tools/embed/w/electrical-power-calculator" title="Electrical Power Calculator by A2Z Tools" width="100%" height="740" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

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How it works

The widget runs the same power engine as the A2Z Single-Phase Power Calculator, using the sinusoidal definitions that IEEE Std 1459 sets out. For AC it first establishes the apparent power S = V x I, then the real power P = S x PF and the reactive power Q from the power triangle, so a 10 A load at 230 V and power factor 0.9 is 2,070 W but still 2,300 VA on the cable. DC is solved as the special case where power factor is 1 and watts equal volt-amps. It can also work backwards from a wattage to the current, or from wattage and current to the voltage, and it reports the phase angle so students can connect the numbers to the triangle.

Calculation method

  • DC: P = V x I
  • AC single-phase (RMS values): S = V x I (VA), P = V x I x PF (W), Q = sqrt(S^2 - P^2) (var)
  • I = P / (V x PF); V = P / (I x PF); phase angle = acos(PF) in degrees
  • Results shown to 2 decimal places; power factor must be above 0 and at most 1

Worked examples

230 V load at power factor 0.9

Inputs: AC, 230 V, 10 A, PF 0.9

Result: 2,070 W real, 2,300 VA apparent, 1,002.55 var reactive, angle 25.84 degrees

S = 230 x 10; P = S x 0.9; Q = 2,300 x sin(acos 0.9).

Limitations

  • Assumes sinusoidal voltage and current; with harmonic-rich loads such as many LED drivers and switch-mode supplies, true power factor differs from cos(phase angle).
  • Single-phase and DC only; it does not check cable, fuse or breaker ratings.

Where publishers use it

  • Appliance and generator retailers showing how many amps a product draws
  • Home-improvement blogs explaining why a 2 kW kettle needs a 10 A circuit
  • Solar and UPS installers helping customers add up loads in watts and VA
  • Electrical engineering course pages on real, apparent and reactive power

Questions

What is the difference between watts and VA?

Watts (real power) is the rate at which energy is actually used. Volt-amps (apparent power) is voltage times current, which is what cables, fuses and UPS ratings must carry. They are equal only when the power factor is 1.

What power factor should I use?

1 for resistive loads such as heaters, kettles and incandescent lamps. For motors, compressors and electronic power supplies use the figure on the nameplate or datasheet - it varies with the design and with how heavily the machine is loaded.

How many amps does a 960 W load at 120 V and power factor 0.8 draw?

960 / (120 x 0.8) = 10 A, and the apparent power is 1,200 VA - the widget shows both, plus 720 var of reactive power.

Does this handle three-phase supplies?

No - three-phase power includes a square-root-of-three factor. Use the three-phase power calculator for that.

Sources

  1. IEEE 1459-2010 Standard Definitions for the Measurement of Electric Power Quantities Under Sinusoidal, Nonsinusoidal, Balanced, or Unbalanced Conditions - IEEE . Definitions of active, reactive and apparent power and power factor

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Electrical Power Calculator
https://a2z.tools/single-phase-power-calculator

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