How to size a UPS (Uninterruptible Power Supply) – Critical Power Solutions

How to size a UPS (Uninterruptible Power Supply)

You have decided that you need a UPS.  What is next?  How do you know which one to pick?  At Critical Power Solutions we are experts in sizing the right uninterruptible power supply for the job. 

To assist with selecting the correct UPS for you, follow the below questions and calculations to help identify your power needs:

  1. List all equipment to be protected by the UPS (remember to include monitors, external hard drives, routers etc).
  2. List the amps and volts for each device.  These ratings can typically be found on the label on the back of the equipment.  Multiply amps by volts to determine VoltAmps (VA).  Some devices may list their power requirements in watts.  To convert watts to VA, divide the watts by power factor.  For servers the power factor is often 0.9.
  3. Multiply the VA by the number of pieces of equipment to get the VA subtotals.
  4. Add the VA subtotals together.
  5. Multiply the total by 1.2 to get the grand total.  This step accounts for future expansion.
  6. Use the grand total to select a UPS.  When choosing a UPS, be sure that the total VA requirement of supported equipment does not exceed the VA rating of the UPS.
If you require assistance in selecting the best UPS for your Home or Business requirements, please get in contact with us today on 1300 277 877 or