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Difference Between Online UPS and OffLine UPS

As the world becomes more reliant on secure data, UPS systems, which supply emergency power to a system if the grid goes down, are becoming an essential part of our lives.  These UPS are categorized into two types: Online UPS and Offline UPS.  

However,what is the difference between online UPS and offline UPS?

There are four main differences as we list below.

Operation difference:

The batteries of offline UPS are charged all the time. If the power fails, the load is powered by the inverter. Lower Cost offline UPS generally, when on inverter/battery backup, provide a square/pseudo sine wave output waveform. 


Online UPS takes the incoming AC mains supply and converts it to DC which feeds the battery and the load via the inverter. If the mains supply fails, then the batteries feed the load via the inverter with no interruption to the output supply at all. It means our electronics get power from the online UPS, rather than directly from the AC mains. Therefore, even if the main AC power fails, the operation of our electronic equipment does not need to be stopped.

What's more, The dual conversion design (AC-DC / DC- AC) of an Online system ensures a far higher degree of isolation of the load from the irregularities on the mains supply. That's why the Online system delivers a fixed and stable output all the time.

Voltage distortion difference:

Online UPS: Voltage distortion does not reduce the performance.

Offline UPS: The more the voltage fluctuations, the more the offline UPS is used. A frequent switch could lead to switching delays or could ultimately reduce its performance.

Price difference:

Compared with online UPS price,offline UPS's are cheaper.

When to use

In situations where a square/pseudo sine output waveform is not acceptable then true sine wave more expensive off-line or  online UPS are recommended.  But when you are much concerned about the cost and wish a lower operating temperature, offline UPS is better.

If you want to know more about the difference, check out our products features: http://www.kstar.com/OnlineTransformerlessUPS/index.jhtml