Inverter Size Calculator

Appliances / loads running together

Appliance / loadQtyRunning W eachStartup / surge W each

Sizing assumptions

Continuous-load design margin

Planning power factor for W → VA conversion

Surge interpretation

Enter startup/surge watts explicitly for loads that need them. Motors and compressors such as refrigerators, freezers, pumps and some air conditioners can require substantially more power during startup. Use manufacturer data or a suitable measured/design value where possible. For a non-surging load, enter its running watts as the surge watts.

Waiting for calculation

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Your inverter planning result will appear here after you click the button.

—simultaneous running load

—continuous design load

—planning continuous VA

—required surge screening

Largest individual startup increment—

Power-factor assumption—

Continuous margin—

Surge scenario—

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Electrical design boundary: This is a planning/screening calculator, not an equipment approval. An inverter must satisfy both continuous output and its manufacturer's stated surge capability for the required duration. Also verify waveform, battery/DC voltage, charger/MPPT compatibility, transfer switching, neutral/earthing arrangement, protection, cable sizing, temperature derating, motor starting method and manufacturer limits. Battery capacity determines backup duration and is sized separately.

How the calculation works

Running load is the sum of quantity × running watts for appliances expected to operate simultaneously. The continuous design load adds the selected margin. Planning VA is continuous watts divided by the entered power factor. For the default startup scenario, the calculator assumes the largest single startup increment occurs while the other loads are already running: total running watts + the largest difference between that load's surge watts and running watts. The alternative scenario sums all entered surge loads simultaneously. These are screening scenarios, not substitutes for equipment-specific surge curves.

How to Use and Check Your Result

Enter the measurements, quantities, costs and assumptions requested in the calculator above. Use its calculation control and review the displayed result. All figures should be checked against your actual project or operating conditions.

Planning and safety: Electrical or power-system sizing requires qualified design review and applicable safety standards. Finelib does not certify engineering designs or supplier quotations.

Frequently Asked Questions

What does the Inverter Size Calculator estimate?

It estimates planning quantities or costs from the figures you enter. Review the calculator assumptions before using the result.

Can I use this calculator for a project in Nigeria?

Yes. Enter measurements and quotations relevant to your Nigerian location and project.

Does Finelib supply current market prices automatically?

No. Prices and rates should be checked with relevant suppliers; do not assume any illustrative values are live quotations.

Are the results guaranteed to be accurate?

No. The output depends on entered assumptions and is intended for preliminary planning, not professional certification.

How should I handle wastage or losses?

Where the calculator provides a wastage or contingency field, enter an allowance appropriate to the project. Otherwise account for it separately.

Can I use the result to request supplier quotes?

Yes. Use Finelib Match to find suitable businesses and request Quotes or Offers, then verify specifications and providers.

Should a professional review the result?

Yes, when the decision involves structural safety, electrical safety, major equipment, significant expenditure or regulatory requirements.