To select the right uninterruptible power system for your application, you need to select a UPS that can support the total load with at least 20% more for load expansion and start-up currents. Load is measured in total load demand Amps multiplied by 230 for a 230Vac single phase supply to give a VA or total Watts. The Amperage ratings can be read on the rear panel rating plates of computers, servers and network devices, or taken from manuals and data sheets. These will be the maximum ratings. Once you have the VA or Watts load, select a UPS form factor i.e. desktop, tower or 19inch rackmount and a solution to provide the backup time you need.