Sizing a UPS. It might seem a bit overwhelming, especially if you want to back up a number of devices via a UPS, but it is more or less just adding up the power demand of each device. Sounds simple!

If a UPS is required to back up a server, a 24-way switch and a router, you have 3 critical pieces of equipment that all ask for power. In this example, the server could have a maximum power demand of 2000 Watts (W), a 24 port switch at 400W and a router at 30W. The total is just adding the 3 devices together and ending with a total potential power demand, here it is 2430W.

Ideally, leaving some room for expansion is beneficial. For this reason, it is our recommendation to not load a UPS above 80% of its capacity when sizing your UPS system. 2430 x 1.2 (adding 20%) equates to 2916W. For this scenario, a UPS system that has a larger power output than 2916W would be suitable.

Most 3000VA online (we’ll get to online technology soon) UPS are unity power factor now. This means that the UPS will output the 3000W without losses - VA = W. Sometimes this will not be the case, so it is always best to check the technical specification, or better yet, consult an expert for guidance.

Now, this is a simple scenario where power demands are easy to calculate and the number of devices is limited. However, there have been many, many occasions where UPS are either oversized (output more than they need in W) and capital is wasted on the investment or undersized which will leave the load vulnerable to power losses.

If you aren’t sure of the power demand, but know that you want to backup a critical circuit, knowing the breaker size will allow you to get an idea of the maximum power that the circuit could demand. Sizing your UPS from that would not leave you far wrong.

Of course, for accurate and real-life power usage, power analysers can be utilised as a reporting tool to showcase exactly what power is being asked for, and when. That’s just one of the many UPS-related services TheUPSTeam Ltd offers.

For help regarding sizing your UPS correctly, or for any other UPS queries you may have, contact our sales engineers today. They are happy and ready to help.