If you're interested in the damages that modified sine waves can cause over long periods versus pure sine waves Google it. There are engineers who have devoted their entire careers to studying this, and can describe it in a much more competent manner than I can If you are running any sensitive electronics, stay the hell away from modified sine. Fans even have a severely reduced lifecyle. Pretty much every high quality inverter that is running an entire home i or business is pure sine. Modified signs are what you see for sale at cheap truck stops. Pure sine is about 2x as much. To keep it in simple terms, a modified sine wave is like choppy water, a pure sine wave is like a smooth flow of current.
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In certain situations, the modified sign can actually be slowly burning up electronics, or causing unusable RF static on a boat, as well as all types of unwanted interference
MSW vs PSW graph.