Quick Answer
Inverter size must handle peak loads—total wattage of all appliances running simultaneously. Add 20-30% margin for motor startup surges. Most homes need 3000-5000 watt inverters. Continuous rating matters more than peak rating for sizing. Budget 20-40% cost premium for quality pure sine wave inverters over modified sine.
Peak Load Calculation
List all appliances with wattage ratings. Identify those running simultaneously—water heater, AC, well pump. Sum total wattage for realistic simultaneous demand. Most homes run 3000-5000 watts simultaneously. Budget oversizing prevents constant operation at maximum capacity.
Motor and Compressor Surge Consideration
Electric motors draw 3-7 times rated wattage during startup. Compressors in refrigerators or AC create large surges. Inverter must handle largest surge in your system. Soft-start devices reduce surge requirements but cost additional. Oversizing inverter 20-30% provides comfortable surge capacity.
Pure Sine vs Modified Sine Wave
Pure sine wave inverters produce clean power matching utility quality. Modified sine wave costs less but damages some electronics. Microwave, medical equipment, and sensitive electronics require pure sine. Budget difference justifies pure sine benefits—reliability and equipment protection.
Location and Heat Dissipation
Inverters generate heat requiring adequate ventilation. Mount near battery bank minimizing cable losses. Proper ventilation prevents overheating and efficiency loss. Location near loads reduces voltage drop in wiring. Installation location matters as much as capacity selection.
Expandability Considerations
Stacked inverters enable capacity increases without replacement. Expandable systems cost more initially but offer flexibility. Fixed systems require replacement when capacity increases. Future expansion planning affects initial investment.
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