Help CenterInverters
Pure sine vs modified sine wave — load compatibility
Inverter3 min readUpdated: 2026-08
The shape of the inverter's AC output directly affects load compatibility. A pure sine wave faithfully reproduces standard grid power; a modified (stepped/trapezoidal) sine wave is cheaper but problematic for some equipment.
| Load type | Pure sine wave | Modified sine wave |
|---|---|---|
| LED, resistive (heater, hotplate) | OK | OK |
| Induction motor (fan, pump) | OK — quiet | Works but runs hot and hums, shorter lifespan |
| Compressor (fridge, AC) | OK | Risky — possible motor overheating |
| Switch-mode charger (laptop, phone) | OK | Usually OK, sometimes audible noise |
| Medical equipment, laser, some VFDs | Required | Avoid |
A modified sine inverter on a refrigerator or AC unit can appear to work for months before compressor overheating causes premature failure. The risk isn't always immediate.
For any project with a compressor, pump, or sensitive electronics, SolarDim Pro always recommends a pure sine wave inverter. The extra cost (10–20%) is far below the cost of replacing a compressor.
Common mistakes
- Choosing modified sine purely to cut the initial inverter budget
- Not checking compatibility for specific equipment (medical, industrial)
- Blaming a compressor failure on a product defect instead of the waveform