Topten China presents the most energy efficient monitors on Chinese market.

1. Scope

Liquid Crystal Display connected to computers.

Screen size is between 15 and 24 inches.

2. Selection criteria

To be selected IN the Topten product list, the monitors must meet national energy efficiency grade 1 requirement, perform in the most efficient way according to the energy efficiency of the computer monitor and off mode power:

Screen Size (SS, Inches)

Energy Efficiency of Computer Monitors (cd/W)

Off mode power (W)













3. Terms

Electricity cost (5 years): The electricity cost of the monitor in 5 years, according to the annual electricity consumption below. The electricity price is set at 1.0 RMB per kWh. Unit: RMB.

Annual electricity consumption: The electricity consumed by the monitor within one year. The typical using time per year of the monitor is set at 2500 hours of on mode. Unit: kWh.

Display size: The diagonal line of the screen display area. Unit: Inch.

Display resolution: The number of distinct pixels in each dimension that can be displayed. Unit: pixel.

Contrast ratio: The ratio of the luminance of the brightest color (white) Resolution to that of the darkest color (black) that the system is capable of producing.

Image format: The ratio of the width of the screen display area to its height. The typical image formats include: 4:3, 16:9 and 16:10.

Brightness:The image’s typical brightness (luminance). Unit: Candela per Square meter (cd/m2).

Backlight type source: Backlights illuminate the LCD from the side or back of the display panel. The typical LCD sources are: LED or CCFL. Generally, the efficiency of LED backlight is higher that the CCFL backlight.

Energy Efficiency of Computer Monitors: The indicator to show the efficiency of the monitor, it’s the ratio between the screen display brightness and monitor power input (also named on mode energy efficiency). The higher of the monitor’s energy efficiency of computer monitor indicator, the better. Unit: Candela per Watt (cd/W).

Energy Efficiency of Computer Monitors = (S × L) / Pw

Pw: On mode power of the monitor, unit: W

S : Monitor display area, unit: m2

L : Screen display brightness, unit: cd/ m2

On mode power: Thepower of the monitor when the monitor is in on mode (working mode). On mode is the operational mode of a display that is (i) connected to an external power source, (ii) has all mechanical (hard) power switches turned on, and (iii) is performing its primary function of producing an image. Unit: W.

Off mode power: Thepower of the monitor when the monitor is in off mode. Off mode is the mode that the monitor is connected to the external power source and the power switch on the monitor is switched off. Unit: W.

National energy efficiency grade: The mandatory grading system for energy using products to disclose the energy performance to the consumers. Grade 3 is the minimum energy efficiency requirement for the market access and Grade 1 is the best for the monitors. Followings are the national energy efficiency requirement:

Monitor types

National energy efficiency grade






Energy Efficiency of Computer Monitors (cd/W)

Off mode power (W)

Energy Efficiency of Computer Monitors (cd/W)

Off mode power (W)

Energy Efficiency of Computer Monitors (cd/W)

Off mode power (W)
















4. References

GB 21520 – 2008 Minimum allowance values of energy efficiency and energy efficiency grades for computer monitors

ENERGY STAR® Program Requirements for Displays Eligibility Criteria (Version 5.0)

5. Data sources

China Energy Labeling Program(

Zhongguancun Online(



All the information presented at Topten China comes from public available information sources. If you think you spot an error, please report to

Producers and retailers are kindly asked to contact about more products which meet the Topten selection criteria.