Enter the inverter output real power (watts), the inverter output voltage (volts, RMS for AC), and the power factor (0–1) into the calculator to determine the Inverter Current. 

Inverter Current Calculator

Enter any 3 values to calculate the missing variable

Inverter Current Formula

This calculator estimates an inverter’s output current from output real power, output voltage, and power factor. For AC outputs, use RMS voltage. For DC output, power factor can be treated as 1.

I = \frac{P}{V \times PF}

From this relationship, output current increases when load power rises, output voltage falls, or power factor drops. That is why low-voltage systems and low-power-factor loads often draw more current than expected.

Equivalent Forms

If you know any three variables, you can solve for the fourth with these rearranged forms:

P = I \times V \times PF
V = \frac{P}{I \times PF}
PF = \frac{P}{I \times V}

Watts, VA, and Power Factor

Real power is measured in watts, while apparent power is measured in volt-amps. Power factor connects the two. If your load is specified in VA instead of watts, convert it before using the calculator.

P = S \times PF

A lower power factor means more current is required to deliver the same real power.

Three-Phase Inverter Current

If the inverter output is three-phase, use the total three-phase real power and the line-to-line output voltage:

I = \frac{P}{\sqrt{3} \times V \times PF}

The calculator on this page is most directly suited to single-phase or DC output calculations. For three-phase systems, use the relation above.

Input Definitions

Input Meaning Typical Unit
Inverter Power Real output power delivered to the load W
Inverter Voltage Output voltage; use RMS voltage for AC V
Power Factor Ratio of real power to apparent power; use 1 for DC and nearly resistive loads Unitless
Inverter Current Output current delivered by the inverter; use RMS current for AC A

How to Use the Calculator

  1. Enter the inverter’s real output power in watts.
  2. Enter the inverter output voltage.
  3. Enter the load power factor between 0 and 1.
  4. Click calculate to find the missing value.
  5. Interpret the result as the inverter’s steady-state output current, not startup surge current.

Example 1

An inverter supplies 1000 watts at 120 volts to a load with a power factor of 0.90.

I = \frac{1000}{120 \times 0.90} = 9.26 \text{ A}

The inverter output current is approximately 9.26 amps.

Example 2

If that same 1000-watt load is supplied at 230 volts with the same power factor, the current falls because the voltage is higher.

I = \frac{1000}{230 \times 0.90} = 4.83 \text{ A}

The output current is approximately 4.83 amps.

Output Current vs. Battery/Input Current

This calculator returns the current on the inverter output side. The DC current drawn from the battery or DC source is different and depends on the DC input voltage and inverter efficiency.

I_{in} \approx \frac{P_{out}}{V_{DC} \times \eta}

For example, if an inverter produces 1000 watts from a 12-volt DC source at 90% efficiency, the input current is roughly:

I_{in} \approx \frac{1000}{12 \times 0.90} = 92.6 \text{ A}

This is why low-voltage battery systems often require heavy cables, large fuses, and tight connections even when the AC load current seems moderate.

Common Mistakes

  • Using apparent power in VA instead of real power in watts.
  • Ignoring power factor for AC loads with motors, compressors, or inductive components.
  • Mixing AC output current with DC battery current.
  • Using nominal voltage when the actual operating voltage is significantly different.
  • Assuming running current and startup or surge current are the same.
  • Using the single-phase formula for a three-phase inverter output.

Why This Calculation Matters

Estimating inverter current is useful when checking load compatibility, comparing inverter operating points, and understanding how voltage and power factor affect current draw. It is also a helpful first step when evaluating conductor loading, connection ratings, and expected thermal stress on the output side of the inverter.

Frequently Asked Questions

What power factor should I enter?
Use the load’s actual power factor if known. For DC output or nearly resistive loads, a value of 1 is commonly used.
Why does a lower power factor increase current?
When power factor drops, more current is needed to deliver the same real power to the load.
Does this calculator include surge current?
No. It estimates steady-state current. Loads with motors or compressors may draw much higher current for a short time during startup.
Can I use this for three-phase output?
Yes, but use the three-phase equation shown above rather than the single-phase form used by the basic calculator.