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How to correctly size a UPS


It is fairly easy to understand why power is so important for companies across the globe – one second without electricity can put a business’ livelihood at risk. Yet for all the focus placed on power nowadays, the factors that should be considered when selecting one a basic piece of equipment – the uninterruptible power supply (UPS) – are often overlooked.

Selecting the right UPS system has less to do with sorting through technology and more to do with knowing the actual needs of the organisation and analysing the size of the UPS required to supply power to critical equipment.
Says Paolo Miglietta, regional channel manager for Africa at APC-MGE: “When contemplating the purchase of a UPS, businesses need to ask themselves how much downtime actually costs them,” he says. “The higher that cost, the more it pays to invest in a UPS and other infrastructure that can assure high availability or system uptime. In fact, correctly dimensioned UPS systems can help save costs and at the same time increase the availability of data centres.”
Sizing a UPS system is a matter of adding up the power requirements of equipment to be protected. This can be done by adding up all of the amps required and multiplying by 220V to get a VA rating. For example, if a PC equals 0.5A and an external modem is 0.5A, the total amps is 1A. Multiplied by 220V, the VA rating would be 220VA. This number represents the  smallest-sized UPS system that should be used and means that the user would need to buy a 300VA UPS for additional runtime.
Alternatively the user can add up the total Watts of the equipment and then multiply the figure by 1.4 for a VA rating.
APC-MGE provides an online sizing tool, which can be accessed via In addition, APC-MGE recently launched the Unit Runtime Calculator, a free pocket-sized guide that assists in finding the best APC solution to suit a user’s needs within seconds and also offers additional batteries for extended runtime.