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Inverter Size Calculator

Pick an inverter that carries everything running at once, with headroom for the worst motor start.

continuous + surge · free · no account

Your load

Recommended inverter

Continuous rating
W
Surge headroom
W
Size the continuous rating to all loads that can run together; surge covers the worst motor start. A real-world guide, not a guarantee.
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Inverter is one piece.

The designer sizes the inverter against your real simultaneous loads, then the battery, solar and every cable to match.

Design my system — free

No account needed to design. Same engine, same standards as this calculator.

How inverter sizing works

The continuous rating must cover everything that can run at the same time; the surge rating must cover the biggest start-up spike (motors and compressors draw several times their running watts for a moment). Size to the continuous figure, then check surge.

Questions

Continuous vs surge?

Continuous is steady draw; surge is the brief spike when a motor or compressor starts — often 2-3x running watts. The inverter must handle both.

Design your whole system — free

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Planning aid — not a substitute for a licensed electrician. Wattonomy sizes to ABYC E-11 / ISO 13297 / BS 7671 / AS/NZS 3008, but every install has factors a calculator can't see. Verify against the hardware datasheets and your local code, and have the work checked by a professional. Improper electrical work can cause fire, injury or death.