What Is Standard THD On A Generator? (Total Harmonic Distortion)

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A THD of 3% is standard THD on inverter generators. Non-inverter generators tend to have THD ratings around 9% to 12% and higher.

You need an inverter generator to safely run sensitive electronics. The high total harmonic distortion of regular machines involves a risk of damage or early wear and tear.

This lower risk of damage to sensitive electronics is typically worth the extra short-term investment.

What is the THD rating of the average portable generator?

Regular portable generators typically have THD ratings of around 9% to 12%. As you can expect, there are definitely also generators that go above these numbers.

Inverter generators tend to have THD ratings below 5% thanks to the built-in inverter. You want to choose this type of generator to power sensitive electronics.

Both of these categories of generators can be portable but their THD ratings can vary to relatively big extents.

What is a good THD rating for a generator?

A good THD rating for an inverter generator is 1.2%. For regular generators, a THD rating of less than 9% is considered to be good but not always low enough.

Inverter generators with a THD rating of less than 5% are typically good enough for sensitive electronics.

Is higher or lower THD better in a generator?

Lower THD tends to be better than higher THD in a generator when it comes to safety and performance.

This will provide your sensitive electronics like computers, laptops, TVs, phones, etc. with electricity that involves a low risk of damage.

The downside of generators with a built-in inverter is that they are more expensive than similar models without one.

However, you will likely prefer investing a bit more in an inverter generator over having to replace your sensitive electronics.

How much total harmonic distortion is acceptable in a generator?

A total harmonic distortion of 5% is typically acceptable in a generator that has to power sensitive electronics.

The total harmonic distortion of a generator matters less for electronic devices like a sump pump. In this case, even 20% THD can be acceptable in a generator.

Additionally, just because an electrical device does not instantly break down, does not mean it is not experiencing the negative effects of higher THD.

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Mats is the founder and head editor of Generator Decision. With a combination of critical thinking, tireless research, and a healthy interest in electronics he helps people find the right generators and how to use these. At this point in the journey, Mats has done research on hundreds of portable generators.