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Solar Inverter Calculator
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This Solar Inverter Calculator recommends an inverter rating (in VA) from your total connected load, a safety margin for surge/startup currents (especially for motors and compressors), and the power factor. Enter the combined wattage of everything you'd run simultaneously, and the calculator scales it up to account for real-world headroom rather than sizing an inverter right at its continuous limit. It's a starting point for sizing a solar or backup inverter system. Everything runs locally in your browser. Scroll down to enter your load details.
Features
- Calculates recommended inverter VA rating from connected load
- Configurable safety margin for surge loads
- Adjustable power factor
- Instant recalculation as you adjust inputs
Why use this solar inverter calculator?
- Avoids undersizing an inverter for real-world startup loads
- No manual VA conversion required
- Fully private — nothing uploaded
- Free with unlimited use
Frequently asked questions
Why is a safety margin needed?
Motors, compressors, and pumps often draw 2-3× their rated wattage for a fraction of a second at startup; a safety margin (commonly 25% or more) helps ensure the inverter can handle that surge without tripping.
What is power factor and why does it matter?
Power factor relates real power (watts) to apparent power (VA) — inverters are rated in VA, so a lower power factor (common with motors and some electronics) means you need a higher VA rating for the same wattage load.
How do I find my total connected load?
Add up the wattage of every appliance or device you'd realistically run at the same time — check nameplate ratings or use a plug-in power meter for accuracy.
Should I size for my peak load or typical load?
Size for your realistic peak simultaneous load (not the sum of everything you own), since that's what the inverter actually needs to handle at once.
Does this replace consulting an installer?
No, this is a planning estimate; a solar or electrical professional should confirm final sizing, especially for systems with significant motor loads.