Inverter Size Calculator
Estimate inverter size in volt-amps.
Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.
Inverter Size Calculator
How to use this tool
- Enter the total load in watts and the power factor.
- Enter a safety margin, then press Generate.
- Use Load sample for 800 W at a power factor of 0.8 with a 25% margin.
Worked example
An 800 W load at a power factor of 0.8 needs 800 / 0.8 = 1,000 VA, and with a 25% margin the recommended size is 1,250 VA.
What this tool does not do / Limits
This is an estimate from the loads you enter, using the stated assumptions. It is not a substitute for an electrician, who must check starting currents, battery sizing and local rules.
Frequently asked questions
Why divide by power factor?
Inverters are rated in volt-amps, and watts equal volt-amps times power factor, so a lower power factor needs a larger inverter.
Does this size the battery too?
No. Battery size depends on how long you need backup, which this tool does not ask for.
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