Which UPS Should you buy?
There are different types of UPS systems, line interactive and online UPS systems, which have different main objectives.
A line interactive UPS will generally clean the incoming utility power by taking care of spikes and brownouts and provide you with a short battery backup period to allow you to safely save your work on a computer and shut down your system. They are not meant to be run for extended periods of time – doing so could cause the unit to fail or could even cause a fire.
Online UPS systems on the other hand provide an off-line power source by converting DC battery stored power back to 220V for longer periods of time – but they are also more costly.