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Pure Sine Wave Inverter vs Modified: What’s the Difference?

Whether you’re trying to live off-the-grid or just maintain your appliances if your power goes out, sine wave inverters will help you convert electrical currents from direct current (DC) to alternating current (AC).

However, when it comes to pure sine wave inverter vs modified, it’s important to know what each is designed for and its parameters. Before you invest, this guide will help you make sure you’re getting the right one off the bat.

Pure Sine Wave Inverters

Both types of inverters will do the same thing, meaning they’ll convert DC electrical currents into AC currents (1). Energy.gov explains this process well:

In DC, electricity is maintained at constant voltage in one direction. In AC, electricity flows in both directions in the circuit as the voltage changes from positive to negative.

However, pure sine wave inverters differ from modified ones because they’ll create AC waves that most closely resemble a sine wave. 

If not attached to real electricity, some devices will only run when plugged into pure sine inverters like those found in solar grid-tie inverters, which is why it’s important to know the difference between a modified vs. pure sine wave inverter.

Modified Sine Wave Inverters

Modified sine wave inverters are similar to pure ones but aren’t the same. Modified inverters create a sine wave that’s easy to produce but not as closely related to actual DC currents (1).

Energy.gov defines modified sine waves like this:

Modified sine wave — A waveform that has at least three states (i.e., positive, off, and negative). Has less harmonic content than a square wave.

Ultimately, modified sine options are highly popular, but you have to be careful because some technology is not compatible with these units.

The inside of an inverter

Comparing the Details: Modified vs Pure Sine Wave Inverters

If you Google, “modified sine wave inverter vs pure” choosing the right one can be difficult; but we’re here to make the process easy. We’ve picked out a few key areas that note the differences between pure and modified sine inverters so you can make your choice quickly and easily.

Cost

Typically, in the battle of “pure sine wave inverter vs modified” pure sine units are more expensive.

This is because pure sine wave power inverters create AC waves that more closely resemble DC electrical currents, which allows them to work with appliances like refrigerators, microwaves, and compressors increasing their overall costs.

Pure sine wave inverters are more expensive than modified inverters but are more versatile.

Modified sine inverters are more cost-effective when used with the right equipment but may not get the job done for others. For example, motors don’t work with modified AC sine waves and can damage the inverter if you attempt to use it (3).

WINNER: When comparing costs between modified and pure waveform sine power supplies, modified style units win due to their simplified design. However, you must choose your unit correctly, because attempting to power the wrong equipment with a modified sine wave inverter can give you more problems than solutions.

Range of Devices Powered

When choosing between modified and pure waveform sine wave inverters there are a couple of things to keep in mind regarding the variety of devices each can power.

Pure AC sine waves can power big appliances like refrigerators, as mentioned above, but can also handle battery chargers, medical equipment, light dimmers, and more sensitive equipment like iMacs, servers, and network equipment.

Modified sine wave units may be less costly than pure ones, but they don’t have the same versatility if you don’t need to power big appliances or items that are sensitive or offer various settings. For example, a drill with many speeds may only operate at high or low if it’s using a modified inverter.

WINNER: At the end of the day, modified sine power supplies don’t have the range that pure wave models do, so this round goes to pure sine wave output machines.

Efficiency

Pure sine inverters and modified sine inverters are incredibly efficient at keeping the items plugged into them running smoothly. However, this depends on you following directions and only plugging in things that each inverter can handle.

Don’t use an inverter for more than it’s capable of handling.

We’ve established that pure AC sine wave inverters cater to a wider range of items than modified sine units, but in terms of efficiency pure sine options win out. Sensitive appliances like microwaves, compressors, and refrigerators that use AC motors will not run as efficiently on a modified sine wave inverter (3).

WINNER: Pure sine wave power inverters. While both machines are very efficient at their jobs when used correctly, the more efficient of the two will be the pure waveform machine. If you’ve got a shortlist of items to plug into an inverter, though (and none of them are sensitive electronics), a modified will work just as well.

Effect on Powered Device

Modified sine wave inverters are the only devices that will affect the running power of a device. On the other hand, pure sine wave power is designed to handle pretty much any device.

This is best explained by this helpful video, where a microwave oven was put to the test:

I won’t give any spoilers, but all I can say is that with modified sine wave inverters you encounter products that “may” or “may not work.” This includes laser printers, photocopiers, devices that use silicon-controlled rectifiers, and many fluorescent lights (3).

WINNER: Pure waveform sine inverters will run equipment just as smoothly as if you plugged it into a full electrical source, so it’s no wonder it wins against modified sine inverters yet again.

Final Verdict

If you’re in the market for an inverter to power more sensitive equipment or major appliances, it’s clear that pure AC sine wave power inverters are the way to go. That being said, it’s not to say modified inverters are inherently bad or won’t get the job done for some equipment – it just means they’re not as versatile by design.

FAQs

To answer the question, if you “really need” a pure sine wave inverter, the short answer is it depends

If you need to power sensitive electronics like desktop computers, servers, and CPAP machines, then you’ll need a pure AC sine wave power inverter. If you need to power basic electronics like a desk lamp, oil diffuser, or table fan, a modified sine wave inverter will do just fine.

The reason why pure waveform sine wave inverters are so expensive is that they allow you to power a wider range of electronic equipment.

For example, pure sine wave inverters could be used to power servers which hold a business’ whole infrastructure. A modified sine wave inverter that “may” or “may not” work could not be trusted with such an important job.

A modified sine wave inverter can power a long list of equipment including most lights (except fluorescent), TVs, microwave ovens, tools, and more (4). In addition, they can power some computers, but there are exceptions. For some laptops, and some monitors, they may experience interference including lines or a hum (4).

For more ways to get the most out of your electronics, and home appliances, check out our homepage here.

  1. Solar Energy Glossary. Retrieved from: https://www.energy.gov/eere/solar/solar-energy-glossary
  2. Solar Integration: Inverters and Grid Services Basics. Retrieved from: https://www.energy.gov/eere/solar/solar-integration-inverters-and-grid-services-basics
  3. Can a Modified Sine Wave Inverter Damage Electronics? Retrieved from: https://www.lifewire.com/modified-sine-wave-inverter-damage-question-534760
  4. Power Inverter FAQ. Retrieved from: https://www.donrowe.com/power-inverter-faq-a/258.htm
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