I wanted to buy a UPS for my PC. I was going over some and I came across a variety of sine waves that different UPSes generate;

  • Stepped Sine Wave
  • Modified Sine Wave
  • Simulated Sine Wave

I know power in the line is Pure Sine Wave (but this is highly unlikely as dirty power flows in the lines in my country). Which of these waves will cause least damage to PC hardware? If you wanna know the specific UPS I am talking of, here they are. Look down for 'Power Protection' and Im talking of the first set of Line Interactive UPS.

  • 1
    What exactly is your question? The UPS should actually filter these waves, and not transfer them to your hardware, I think you are worried about nothing.
    – Ramhound
    Oct 24, 2012 at 13:04
  • The spec says that these ARE the output waveforms
    – A User
    Oct 24, 2012 at 13:05
  • 1
    The UPS should actually present a sine wave to the downstream side. It does filter out variability in the upstream side, but the downstream components (PC, Monitor, etc.) expect and need a sine wave (AC) coming to them.
    – EBGreen
    Oct 24, 2012 at 13:10
  • Having said that, it is unlikely that the method that the UPS uses to present a produces waveform will make much difference either way.
    – EBGreen
    Oct 24, 2012 at 13:12
  • 1
    possible duplicate of When do I need a pure sine wave UPS?
    – fixer1234
    May 11, 2015 at 16:03

1 Answer 1


For a computer you want a smooth as possible sine wave.

Answering this because in 2021 it was one of the top results on my google search, and so was this article.

About 3/4 of the way down in that article it says:

When the UPS is in normal mode, it passes the same electrical sine wave to your connected devices. If the UPS switches to operate in battery mode, it either produces sine wave or simulated sine wave electricity to power your electronics.

It goes on to say:

You will need a UPS with sine wave technology if you want to plug-in the following:

  • Apple iMac Computers
  • Computers and Equipment that are Energy Star® or 80 PLUS® efficient systems using Active PFC power supplies.

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