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Inverter Sizing

Most undersized inverters are undersized for surge, not for running load. A compressor's locked rotor current can demand three times the continuous rating for a few seconds. This calculator sizes for both, and shows what a soft start would save you.

What it asks for

  • Total continuous running load (W) — Everything that can be on at once, not the whole panel.
  • Largest motor LRA (A) — Off the compressor nameplate. Enter 0 if there is no motor load.
  • Motor voltage (V)
  • Motor start type
  • Future headroom (%) — EV charger, heat pump, shop. 25% is a good default.