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Also known as ‘Active Standby’, ECO mode is the most energy efficient UPS operating mode. Capable of exceptional efficiency up to 99%, ECO mode sees the bypass line (raw mains supply) power the load, with the inverter powered but remaining off as long as the mains is in tolerance.  

It is similar to the basic operating mode of an offline UPS, where the inverter is on standby and ready to switch on if there’s a power problem.  

When there’s an issue with the mains supply, the load experiences a fractional break in supply (perhaps up to 15ms), while the UPS system switches back to the inverter.  

This short break in continuous power is the main drawback to using ECO mode, particularly with sensitive equipment. Another disadvantage of ECO mode is the lack of power conditioning provided by true double conversion online UPS mode. 

The main benefit of ECO mode is the increased efficiency of the bypass line, which typically runs at 98-99% compared to standard online UPS efficiency of 94-97%. This efficiency improvement delivers significant energy savings, particularly in cases where it can be used overnight when any critical loads are inactive.  

ECO mode is only recommended on sites where the utility supply is relatively stable and the load isn’t sensitive to any mains interference. 


What Is Active ECO Mode? 

In recent years, some UPS systems (such as Riello UPS’s NextEnergy range) now offer an operating mode called Active ECO Mode.  

Just like in standard ECO mode, the load is powered through the bypass line (mains). But with Active ECO, the inverter remains on at all times and runs in parallel with the input without actually carrying the load.  

In the event of a mains failure, the inverter takes over far quicker in Active ECO mode, meaning it offers higher availability than standard ECO mode.  

Obviously, the efficiency using Active ECO is slightly less (around 1%) than it is with pure ECO, but this is still considerably better than online, so offers users something of a happy medium. 


Learn more about ECO mode and other UPS operating modes such as Smart Active or Frequency Converter by watching our fun and fact-filled ‘UPS Basics’ video: 



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