Most computer grade UPS have square/modified square sine wave output waveforms. Although perfectly acceptable for most computer based applications, there are some equipment that will perform poorly or simply not work at all.
Originally Posted by Shadow_Ferret
Pure sine wave UPSes use better quality inverters to regenerate an AC waveform with utmost fidelity.
Factors such VA rating, rated current, etc. that are also important and affect price as you go to higher application needs. That is why it's important to size your UPS accordingly for its intended use.
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