Home › Calculators › Inverter size

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

Continuous load — everything that can run at once (W)

Largest start-up surge — biggest motor/compressor (W, optional)

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.

Got your answer? Share or save this exact result — the link reopens with these numbers.Copied to clipboard

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

About a minute. No account, no email.

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.