Size The size of the UPS you need is based on two factors: How long you need things Showbox to be operational after utility power is lost Your power usage Before you can even decide what size you need, you MUST know your average power usage under normal load after boot up. Sarkari Result Get a Kill-A-Watt and measure each piece of equipment (not the entire rack at once) and then add up everything to determine how many watts you are actually using. We'll get to the other factor in a bit. Pure Sine Wave vs Modified Sine Wave Modified Sine Wave systems may (and probably will) have issues with server power supplies. Specifically, they may appear to hold your Pnr Status load while on utility power but when the system switches to battery the load will double (or more) and likely will cause the UPS to shut down instantly. Pure Sine Wave systems do not have this problem but are a little more expensive.