# Total Harmonic Distortion (THD)

A measure of how far the inverter's output waveform departs from a clean sine wave, expressed as the percentage of total signal energy sitting at harmonic frequencies rather than at the fundamental. Lower is better.

Source: https://inverterdata.com/en/glossary/total-harmonic-distortion/
Site: InverterData (inverterdata.com) — open technical specification database
Last updated: 2026-08-24
License: free to quote with attribution to inverterdata.com

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Harmonics do no useful work but still heat cables, transformers and motors, and they can interfere with sensitive electronics and with utility metering. Grid codes generally require current distortion to stay below a few percent at rated output, and good grid-tied inverters comfortably beat that. Two caveats when comparing data sheets: THD is usually quoted at full load and rises at low power, and some manufacturers quote voltage distortion while others quote current distortion. The figure only becomes a practical concern in weak grids or where many inverters share one connection point.

## This spec across the catalog

Recorded on 35 models in this database, from 2 % to 3 %, averaging 2.97 %.