How to Tell if an Inverter is Pure Sine Wave

By:Michael Johns

It’s not always obvious if an inverter is pure sine wave but it’s very important to find out.

The type of power inverter you have directly affects what appliances you can safely run.

There is a big difference between a pure and modified sine wave inverter.

And if you have bought a product second-hand, in a clearance sale, from eBay, or elsewhere it could be missing the technical specification.

In the past, I have purchased an inverter from a Walmart sale, the product was cheap as it was missing the box. 

The only problem was that there was nothing to indicate on the inverter itself whether it was pure sine wave.

So how do you tell if an inverter is pure sine wave?

3 Ways to Tell if Inverter is Pure Sine Wave

In my experience, there are 3 easy ways to test if your inverter is pure sine wave. You can use extra equipment, deal with the manufacturer, or even just listen to the sound it makes.


By far the best way to determine the output of your inverter is with an oscilloscope. An oscilloscope is a device that can observe electric signals and show their waveform on a screen. With this equipment, you can hook up to your inverter a get an instant reading! They come in various shapes and sizes but you won’t need anything too complex for your inverter. In fact, you can get small handheld devices or even multimeters with an oscilloscope function.

How to test an inverter with oscilloscope

Here’s a helpful video to show you how to test your inverter:

Check Manufacturer Information

Another quick way to get more information about your inverter is to contact the manufacturer directly. Quite often you will be able to find technical information and user manuals published on company websites. A really easy way to do find this is by searching the model number manual on Google. Just like this! 

Pure sine wave found in user manual

At the very least, your inverter should have a model number to contact the inverter brand to get more information.

Listen to Sound

One big benefit of pure sine wave inverters is that the smooth current reduces the total harmonic distortion. In simple terms, this means they are less noisy compared to modified sine wave inverters.

If you plug in a device with an AC motor in it such as a small fan you will be able to distinguish the difference. A pure sine wave inverter will not make a buzzing sound! 

Check out this comparison video so you know what you’re listening for:


#1 reason why investing in a better inverter is important #offgrid #vanlife #carcamping #power #budget

♬ original sound – zach

Final Words on Testing if an Inverter is Pure Sine Wave

If you’re planning to run sensitive electronics or inductive loads from your power inverter then it’s crucial to know if it’s pure sine wave.

Things like medical devices, compressors, refrigerators, LED TVs all need pure sine wave otherwise you risk damage and overheating. Plus they won’t work efficiently.

So if you’re not sure what output your inverter delivers then take the time to find out.

You can do this with specialist equipment like an oscilloscope, checking product manuals, or just by listening closely.

Want to know more about different sine wave? Take a look at my Complete Guide to Pure Sine Wave Inverters