RV OWNER’S FIELD GUIDE · SOLAR & POWER
Inverter Sizing Guide
An undersized inverter trips constantly. An oversized one wastes standby power every hour of every day. Size it to what you actually run.
Continuous Load vs. Surge Load
Every AC device draws a running wattage, but motor-driven devices (compressor fridges, microwaves, power tools, some water pumps) draw a much higher surge for the first fraction of a second on startup — often 2–3x the running wattage. Your inverter’s continuous rating needs to cover everything running at once; its surge rating needs to cover the largest single startup spike on top of that.
Microwave: 1,000–1,500W running
Compressor fridge: 60–180W running, 300–600W surge
Coffee maker: 800–1,200W running
Hair dryer: 1,200–1,800W running
Laptop charger: 60–100W running
Pure Sine vs. Modified Sine
Modified sine inverters are cheaper but run some electronics hot, cause audible buzz in certain devices, and can outright damage sensitive equipment like CPAP machines or variable-speed motors. Pure sine is the standard for any modern install and is what Victron and other quality inverter/chargers use.
Don’t Forget Standby Draw
A larger inverter left on 24/7 draws more idle current just staying awake, even with nothing running. If you’re not running large loads constantly, an inverter with a low-power search/standby mode (most quality units have one) meaningfully extends battery life between charges.