Offline, Online and Line-interactive UPS: The Differences

Offline, Online and Line-interactive UPS: The Differences

With paper documentation rapidly going out of fashion, we increasingly depend upon digital data storage. Whilst this streamlines many common systems, there is always the risk of an interruption to the electrical power supply, which can cause great harm to data, even destroying it completely. This is where UPS (Uninterrupted Power Supply) solutions come to the fore, helping to protect your company’s precious data in the event of an interruption to the electrical power supply.

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We tend to think of interruptions to the power supply coming in the form of blackouts or brownouts, but according to Power Electronics, this is not the case. In fact, most problems come in the form of sags, spikes, surges, overvoltage and noise, all of which can cause damage to electrical equipment and the potential loss of data.

UPS solutions come in three forms – offline, online and line-interactive. The question is, which is most suitable for your particular requirements?


Offline UPS is the best solution where any loss of data would be an inconvenience, and where cost is a major factor, as this is the least expensive option. The incoming supply from the mains is directed through a relay contact to the output. When a failure to the mains supply occurs, the UPS turns on the inverter, switching the output relay directly to the inverter, thereby supplying power through its own stored battery supply. There is a brief delay while the mains failure is detected before the battery supply kicks in, making it the least reliable form of UPS.

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Online UPS is necessary where any loss of data would be catastrophic. As soon as there is an interruption to the power supply, the batteries act to maintain power to all systems, seamlessly transferring to power storage as soon as the service is restored. Because of the expense it’s worth researching your UPS requirements carefully before committing to any system – you can view a number of options through online retailers such as, who specialise in Eaton UPS Systems.


Line-interactive UPS is a mid-price solution, ideal where data loss is not catastrophic. The system allows for prolonged brownouts and even surges without impacting on the stored power within its batteries. It can, however, allow for occasional disruptions to service, which needs to be factored in when choosing an appropriate system.

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