Size a DC-to-AC inverter for off-grid solar, battery backup, or mobile power systems. Computes the required continuous VA rating from total load watts and power factor, estimates surge capacity for motor-starting loads (3-7x rated power), applies NEC-recommended 20% derating for continuous operation, and selects the nearest standard inverter size. Also calculates DC input current at the system voltage for cable and fuse sizing. Chain from solar_load_audit to get peak_watts and largest_load_watts, then chain to wire_gauge or wire_ampacity to size the DC cables. Essential for off-grid cabins, RV/van builds, emergency backup, and solar+battery installations.

Total continuous load in watts. Sum of all appliances that may run simultaneously. Chain from solar_load_audit.peak_watts.

Peak surge/starting load in watts. Motors and compressors draw 3-7x rated watts on startup. If omitted, estimated as 3x the largest single load or 2x continuous, whichever is greater.

Wattage of the single largest appliance. Used to estimate surge if surge_watts is not provided. Chain from solar_load_audit.largest_load_watts.

DC system voltage. 12V for small/mobile, 24V for medium, 48V for large residential/commercial. Higher voltage = lower current = thinner cables.

Power factor (0.5-1.0). Resistive loads (heaters, lights) are ~1.0. Motor loads (fridge, AC, pump) are 0.6-0.8. Mixed loads typically 0.8.

Inverter efficiency (0.5-1.0). Good pure-sine inverters are 0.90-0.95. Modified-sine are 0.85-0.90. Budget units may be lower.

Derating percentage for temperature, altitude, and safety margin. NEC recommends 20% (80% continuous rating). Range 0-50%.