Inverter Size Calculator
Calculate the continuous and surge inverter capacity you need, based on the AC appliances you plan to run and which ones run at the same time.
List the AC appliances you might run through an inverter, with their running (continuous) watts and starting/surge watts if known. Tick "runs at the same time" for anything you'd realistically use simultaneously.
| Appliance | Running W | Surge W | Simultaneous | |
|---|---|---|---|---|
Recommended Inverter Size
Continuous requirement
≥ 1,050 W
Surge requirement
≥ 1,300 W
Surge (starting) power is calculated as everything else running continuously, plus the single highest surge draw among your simultaneous appliances. Motors, compressors and some appliances can require substantially higher starting power than their running wattage — always check the manufacturer's specification for anything with a motor or compressor. This tool provides a planning estimate only and is not electrical installation advice.
Continuous vs surge power
Continuous (running) power is what an appliance draws once it's up and running. Surge (starting) power is a brief spike — often much higher — that motors, compressors and some electronics draw for a fraction of a second to a few seconds at startup. An inverter needs enough continuous capacity for everything running at once, and enough surge capacity to handle the highest startup spike on top of everything else already running.
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Frequently Asked Questions
What size inverter do I need?+
Enough continuous capacity to cover everything you'll run simultaneously, plus enough surge capacity for the highest startup spike among those appliances — add your appliances above for a figure specific to your setup.
Why does my compressor fridge need so much surge power?+
Compressor motors typically draw 2-3x (or more) their running wattage for a brief moment at startup. If your inverter can't supply that surge, the fridge may fail to start even though its running wattage is well within the inverter's continuous rating.
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