Why inverter sizing matters more than panel sizing
You can under-size the solar array by 10% and the only penalty is slightly longer charging time. You under-size the inverter by 10% and it shuts down every time the AC compressor kicks in. Inverter sizing is the single most common field mistake in residential solar, and it's the easiest to avoid if you account for surge and motor loads from day one.
The formula our calculator uses
Required VA = (Running load × Diversity factor × (1 + Headroom)) ÷ Power factor. Then we compute surge requirement = Running load × (1 + motor% × 2). Finally we snap the result to the next standard inverter size. Any inverter you shortlist should handle both the required VA and the peak surge for at least 3-5 seconds.
Topology decision tree
- Pure sine wave: Always the safe default. Required for any motor load, microwave, or sensitive electronics. 2026 price premium is minor.
- Modified sine wave: Only for resistive loads (bulbs, chargers). Cheap but destroys motors and creates audible buzz in transformers.
- Grid-tied (on-grid): Required for PM Surya Ghar net metering. No battery, exports excess to grid.
- Hybrid: Best of both — grid-tied + battery backup. 20-30% more expensive but future-proof.
Get the sizing chain right by starting with the Appliance Load Calculator to lock in your running and surge load, then use the Battery Size Calculator to match Ah capacity for hybrid or off-grid setups.