Generator THD: Total Harmonic Distortion, Explained

What total harmonic distortion means on a listing

Total harmonic distortion, or THD, is a term that some generator listings carry as a percentage. It describes the shape of the generator's output compared with a pure sine wave, the waveform that comes from the power grid. A lower percentage means the output is closer to that shape, and a higher percentage means the output has more distortion combined with the main wave. It is a technical description, not a promise of a measured result, and the exact meaning is set by the maker who states it.

This site's catalogue states the generator type, the fuel, the first watts figure grouped, electric start, RV ready, a CO sensor and the brand. It does not state a measured THD figure, because the catalogue carries no measured output data. You read a THD figure on the listing itself and on the maker's page for the model.

Where a THD figure appears on a listing

A THD figure usually appears on a listing for an inverter generator, one of the types this site lists. The listing title names the type, and the maker's page gives more technical detail, including a THD figure when the maker states one. An open-frame generator listing may not state a THD figure at all.

When a listing states a THD figure, read the maker's page to see what the figure refers to. A maker can state a figure under a particular operating condition, and the listing may not repeat that condition. Inverter vs Portable Generator for Texas Homes.

Which electronics makers describe as preferring a pure sine wave

Some makers describe certain electronics as designed for a pure sine wave. A generator whose output is closer to a pure sine wave is what the maker describes for that equipment. The maker's page for the model names the equipment, so check it rather than guessing from the watts figure alone. For a home backup before a Texas winter storm, the question is which generator type a listing names, not which percentage is best.

The site gives no appliance tables, no wattage worksheets, and no statement about how any generator affects a particular device. Whether a unit suits a device is a question for the maker and, where the home wiring is involved, a licensed electrician. The difference between pure sine wave and modified sine wave outputs is explained in general terms there.

What this site can and cannot state about THD

This site compares listings on the stated details only. It carries no measured THD figure, runtime, fuel use, charge time, cycle count, noise, weight or outlet data. When a listing shows a THD figure, the number comes from the maker and belongs in the listing description.

The site also does not state how a THD figure changes the output, because that measurement is not part of the catalogue. You can compare the type, fuel, watts group and features that the listing states, then read the maker's page for the technical figure. Running watts and starting watts are two other listing terms explained there.

Shopping for a THD figure for a Texas home

Before winter storm season or summer heat, a Texas homeowner may shop for a generator and see a THD figure on an inverter listing. The shopping situation matters more than the figure alone: a close neighborhood, a rural home, a home on a propane tank, or a whole house versus essentials choice points to a different type of generator.

For the THD figure itself, the maker is the authority on how it was measured. You can also ask the maker what equipment the figure applies to. The best inverter generator choices for Texas neighborhoods start from the type on the listing, not from a THD number.

• The first watts figure grouped in the listing title
• The fuel type: gasoline, propane, or both on a dual fuel listing
• Electric start, RV ready, CO sensor and brand as stated words
• The THD percentage on the maker's page, when the maker states one

The Texas shopping questions around generator type

A generator type in the listing title, whether inverter, portable or standby, is the starting point for a THD discussion. An inverter listing is where a THD figure usually appears, and a standby listing rarely states one because a standby unit is installed and connects through home wiring, a question for a licensed electrician and the local permit office.

For a first generator before a Texas storm season, read the listing for the first watts figure, the fuel and the features, then check the maker's page for the technical figure. Mid-size generators for home essentials and dual fuel choices for a propane tank are two starting points.

What to pick for your situation

Questions

What is total harmonic distortion on a generator listing?

THD is a percentage stated on some listings that describes the output waveform. A lower figure means the output is closer to a pure sine wave. The number is read on the listing and the maker's page.

Do all generator listings state a THD figure?

No. THD figures usually appear on inverter generator listings, not open-frame ones. The maker decides whether to state one, so read the listing and the maker's page.

Which devices do makers describe as needing a pure sine wave?

Makers name the equipment on their own pages. This site does not list which devices need a pure sine wave, because the catalogue carries no such data. Read the maker's page for the model.

Can a THD figure tell whether a generator will run household appliances?

No. A THD figure describes the waveform, not the capacity. Capacity questions go to the maker and, where wiring is involved, a licensed electrician.

Where should the THD figure be read in a listing?

Read the listing description for the percentage, then read the maker's page for the same model to see what the figure covers. The catalogue carries no measured figures.

Why do THD figures appear on inverter generators?

An inverter generator converts the engine output into a new waveform, and makers often state a THD figure for that output on their pages. An open-frame generator listing may not state one.