Inverter Power Calculator for an Apartment Building

Enter the total power and, if available, the starting power of the largest motor. The result is indicative.

This is an indicative estimate, not a power supply design. Elevators, pumps and motors need an engineering calculation. Installation and connection must be done by qualified specialists only. The platform does not accept funds.

Sum of the rated power of the appliances that must keep running during an outage. Allowed range: from 1 to 1,000,000 W.

If there are motors, pumps or elevators, enter the starting power from the nameplate. If unknown, leave empty. Allowed range: from 1 to 10,000,000 VA.

Number of phases of the loads.

The share of power actually used on average. If you are not sure, leave 100. Allowed range: from 1 to 100 %.

From the load nameplate, 0.1 to 1. If empty, a conservative assumption of 0.8 is used. Allowed range: from 0.1 to 1.

Your result

Fill in the form and press 'Calculate'.

Calculation example

Fictional input data for illustration. This is not a real building and not a recommendation.

Input data: Total power of critical loads: 4000 W; Surge (peak) apparent power: 9000 VA; Connection: Single-phase; Simultaneity factor: 100 %; Power factor (cos φ): 0.9.

Result
IndicatorValue
Continuous inverter power, at least4 000 W
Running apparent power, at least4 445 VA
Peak power with safety factor11 250 VA
Phasessingle-phase
An engineering calculation is required: the result is incomplete or depends on unconfirmed data.

The result is indicative and is not a power supply design or a promise of backup duration.

  • The result is indicative: an engineering calculation is required.

Calculation module version: 1.0.0.

How it is calculated

  • Running apparent power = power / cos φ.
  • Peak power = (running apparent power − starting load + starting power) × safety factor.

Assumptions (unconfirmed, replace with equipment data)

  • A safety factor of 1.25 is an unconfirmed assumption.
  • Without cos φ, 0.8 is used.

Limitations

  • Overload duration, short-circuit current, phase distribution and protective devices are not determined.
  • Three-phase systems and motors require an engineering calculation.

Frequently asked questions

Why is the starting power needed?

Motors draw several times more power when starting than when running; the inverter must withstand this.

What if the starting power is unknown?

Leave the field empty: the result will be marked as incomplete and as requiring an engineering calculation.

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