UPS S-ECO Mode: An Energy-saving Revolution for Data Centers

Data centers are fundamental for the digital economy. As energy prices continue to rise and industries endeavor to chase green goals, there is an increasing demand for green data centers.  

How to optimize data center energy usage and lower power usage effectiveness (PUE)? Uninterruptable Power Supply (UPS) products in more efficient operation modes have a key role to play. The innovative S-ECO mode offers advantages over the standard ECO mode, balancing the need for ultrahigh energy efficiency and system stability.

Challenges in Traditional UPS modes

UPS is a core component of data center backup power. It is used to provide stable power quality to mission-critical applications and supply backup power to the load in the event of a power disruption. However, while providing a reliable source of power UPS consumes nearly 10% of the total energy for a data center facility. It is urgent to improve UPS efficiency through technological upgrades.

A traditional UPS in online double conversion mode converts utility power through the rectifier and inverter, which then supply high-quality power to loads. This mode features high reliability but low efficiency and high-power consumption.

The ECO mode can be used when the online double-conversion mode cannot meet the requirement for higher UPS efficiency. Operating in the ECO mode, the UPS supplies power to loads through the static bypass, which is equivalent to a direct supply of utility power. However, the standard ECO mode is unable to provide 0 ms switchover and has the problem of harmonics  compensation, which compromises the stability of the system.

To address issues in the traditional ECO mode and provide ultimate power system performance, Huawei developed the advanced S-ECO mode.

What is the S-ECO Mode?

The S-ECO mode is a TÜV-certified mode for Huawei’s UPS system that provides zero transfer time between different operation modes while delivering up to 99.1% efficiency. It optimizes the power supply architecture and logic. The mode is activated to solve the problems of low system efficiency in the online double-conversion mode, and output interruption, large harmonics, and input surge voltage interference in ECO mode. The S-ECO mode provides the following benefits: zero transfer time between different operation modes, high efficiency in the full load range, high-voltage surge suppression, and active harmonic compensation.

First, 0ms interruption between different operation modes. When the UPS works in S-ECO mode, it automatically detects power fluctuations of the bypass input. When the bypass input is normal, the bypass supplies power. When the bypass input is abnormal, the UPS transfers to inverter mode seamlessly. It complies with the dynamic response level of class 1 defined in IEC 62040-3. The UPS automatically transfers back to bypass mode once the bypass recovers.

Second, the S-ECO mode delivers high efficiency in the full load range. When the bypass supplies power, the UPS power consumption is extremely low, and the system efficiency is greater than 99.1% at its peak or 98.5% when the load rate is above 20%.

Third, the S-ECO mode suppresses high-voltage surges. When the bypass supplies power directly, the surge voltage of the bypass input is easily transmitted to load ports. To address the high surge voltage, the S-ECO mode uses the high and low voltage clamping technology to compensate for voltage when it decreases and absorb voltage when it increases. It has been verified that the output voltage meets IEC 61000-4-5 requirements on surge voltage.

Fourth, the S-ECO mode implements active harmonic compensation. The power supply units in IT equipment provide the power factor correction (PFC) function. When the input power factor (PF) is good (> 0.9), the bypass can supply power directly. However, mechanical and cooling equipment, such as air conditioners, fans, and water pumps, do not have the PFC function. When the bypass supplies power directly in the traditional ECO mode, reactive power and high-order harmonics are generated and flow into the power grid, which increases the line loss, accelerates the insulation aging, and shortens the equipment service life.


The S-ECO mode can ensure stable and reliable power supply to various loads in data centers and mission-critical power supply in different industries. According to the recently-published UPS S-ECO Technology White Paper, the UPS S-ECO mode can improve the UPS system efficiency by 3%–4% and reduce the PUE by 0.03–0.04, which is equivalent to 1.5 to 2 million kWh of electricity saved each year. If all 10 MVA or larger data centers use this technology, billions of kWh of electricity will be saved each year.

The highly efficient UPS operation mode will facilitate green transformation and trigger an energy saving revolution for data centers. To know more about the S-ECO mode, please visit 


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