Comparison · 5 min read
Pure sine wave vs modified sine wave: what your appliances feel.
Waveform quality decides whether motors hum, run hot, or run normally. A brand-neutral comparison of output waveform, appliance safety, efficiency and cost.
Every inverter converts DC into AC. The difference is how closely that AC resembles the smooth wave the grid delivers and your appliances were designed for.
The gap matters most for anything with a motor, a compressor, or a sensitive controller.
We compare technologies, not consumer brands. Within each technology the honest differences between reputable manufacturers are far smaller than the difference between the right and wrong technology for your usage.
At a glance
| Attribute | Pure sine wave | Modified / square wave |
|---|---|---|
| Output waveform | Smooth sine, close to grid quality | Stepped approximation |
| Motors and compressors | Run at rated efficiency and temperature | Run hotter, draw more current, buzz |
| Fans | Silent, full speed control | Audible hum, reduced life |
| Electronics and chargers | Safe | Some chargers and adaptors fail early |
| Efficiency under load | Higher | Lower — wasted energy shows up as heat |
| Audible interference | Negligible | Common on audio and older TVs |
| Upfront cost | 10–25% higher | Lower |
Strengths, trade-offs and price
Pure sine wave
₹9,500 – ₹68,000
Home units through high-capacity home UPS.
- Safe for refrigerators, pumps, mixers and medical devices
- Appliances run cooler and last their designed life
- No hum from fans or audio equipment
- Higher effective efficiency, so batteries last longer per cycle
- Costs more than an equivalent modified sine unit
Best for: Any home running a fridge, a pump, or anything with a motor — that is nearly every home.
Modified / square wave
₹6,500 – ₹14,000
Entry-level home units only.
- Lowest upfront cost
- Adequate for resistive loads — incandescent lights, simple heaters
- Shortens motor and compressor life
- Audible hum from fans and transformers
- Some adaptors and chargers fail prematurely
- Wasted energy as heat means less real backup per charge
Best for: Very light, purely resistive loads where the saving genuinely matters.
Decide with numbers
Size it before you choose it.
Enter your actual appliances and outage pattern — the calculator sizes the system before anyone quotes you a number.
Our engineering verdict
The price gap between the two is typically smaller than the cost of one prematurely dead refrigerator compressor.
We only fit pure sine wave units for home and commercial backup. If a quote is unusually cheap, check the waveform line on the specification before you compare anything else.
Questions we get asked
Can I run a refrigerator on a modified sine wave inverter?
It will start, but the compressor runs hotter and draws more current than it was designed for. Over years that shortens its life measurably. Use pure sine wave for anything with a compressor.
How can I tell which one I have?
The specification sheet states the output waveform. A practical hint: fans that hum audibly on backup but run silently on grid usually indicate a modified sine wave output.