Display energy efficiency testing determines the on-mode, sleep-mode, and off-mode power consumption of monitors, televisions, and digital signage in accordance with international and regional energy regulations. Using standardized procedures defined by IEC, EN, and GB standards, accredited third-party laboratories measure power draw, luminance, luminous efficacy, and energy efficiency indices to support certification, regulatory compliance, and product development. This guide explains the applicable standards, test items, sample requirements, measurement methods, and common questions related to display energy efficiency determination.
Technical Overview
Display energy efficiency testing is the systematic measurement and evaluation of the electrical power consumption of electronic display products across all operating modes, including on mode, sleep mode, and off mode. The measured data are compared against minimum allowable values (MAVs), energy efficiency grades, or energy efficiency index (EEI) thresholds defined by national and regional regulations. Test results determine whether a product can legally enter a given market, what efficiency grade or label class it may claim, and whether it qualifies for voluntary programs such as ENERGY STAR certification. Because display power consumption is highly sensitive to screen size, panel technology, backlight design, and firmware settings, all measurements must follow strictly standardized procedures to ensure reproducibility and mutual recognition between markets.
Scope of Products
Energy efficiency determination applies to a wide range of display categories, including computer monitors, flat panel televisions, commercial signage displays, interactive whiteboards, and the display subsystems of all-in-one desktop computers. Panel technologies covered include LCD (edge-lit and direct-lit LED backlights), OLED, QLED, and emerging mini-LED and microLED architectures, from small desktop monitors up to large-format video walls and outdoor signage.
Key Standards and Regulations
- IEC 62087 — Methods of measurement for the power consumption of audio, video, and related equipment, defining the dynamic broadcast-content video signal used for on-mode measurement.
- IEC 62301 — Measurement of standby power, applicable to sleep mode, off mode, and passive standby conditions.
- EN 62087 and EN 62301 — European adoption of the corresponding IEC measurement standards.
- Commission Regulation (EU) 2019/2021 — Ecodesign requirements for electronic displays, including EEI limits and standby power caps.
- Commission Delegated Regulation (EU) 2019/2013 — EU energy labelling of electronic displays (A to G classes and EPREL registration).
- GB 21520-2015 — Minimum allowable values of energy efficiency and energy efficiency grades for computer monitors in China.
- GB 24850 — Minimum allowable values of energy efficiency and energy efficiency grades for flat panel televisions in China.
- ENERGY STAR Displays specification — Voluntary program requirements for typical energy consumption (TEC) and luminous efficacy.
- California Title 20 and Title 24 appliance efficiency regulations — Mandatory requirements for monitors and signage displays sold in California.
Testing Samples
Computer Monitors
Desktop and professional monitors of all screen sizes and aspect ratios, measured in their as-shipped configuration with the factory-supplied power adapter and stand. Products with automatic brightness control (ABC) sensors may require supplementary testing with the sensor at defined ambient light levels.
Televisions
Flat panel televisions, including SDR and HDR capable models and hotel/hospitality TVs. HDR models tested under EU regulations require additional peak luminance ratio measurements to justify any applicable allowances.
Commercial and Digital Signage Displays
Large-format displays, video wall panels, interactive touch displays, and outdoor digital signage, often evaluated under dedicated commercial display test conditions including higher default luminance settings.
All-in-One Computers
The integrated display portion of all-in-one desktop systems, where applicable regulations require the display subsystem power to be characterized separately or under combined computing and display load scenarios.
Sample Requirements
Certification testing typically requires one to three production-representative units per model, complete with power cords, adapters, remote controls, documentation, and default factory settings. Model families sharing the same panel, backlight, and power supply platform may be covered by a representative configuration test, subject to the rules of the target program.
Testing Items
The core measurement parameters for display energy efficiency determination include the following items, selected according to the target standard or regulation:
- On-mode power consumption (W), measured with standardized content or test patterns.
- Typical Energy Consumption (TEC), expressed in kWh per day or kWh per year.
- Energy Efficiency Index (EEI) for EU ecodesign and energy labelling compliance.
- Luminous efficacy (cd/W), calculated as average screen luminance multiplied by active screen area divided by on-mode power.
- Energy efficiency value (cd/W) and grade classification (Grade 1 to 3) per GB 21520.
- Sleep-mode power consumption (W).
- Off-mode and passive standby power consumption (W).
- Networked standby power (W) for displays with network connectivity.
- Average screen luminance (cd/m²) and luminance uniformity across defined measurement points.
- Automatic Brightness Control (ABC) luminance reduction verification.
- Peak luminance ratio for HDR-capable displays under EU requirements.
Testing Methods
Test Setup and Environmental Conditions
Testing is performed in a controlled environment at 23 °C ± 5 °C with relative humidity within the range specified by the applicable standard. Luminance measurements are conducted in a darkened enclosure to prevent ambient light interference. The display is supplied from a stabilized AC source at the rated voltage and frequency of the target market (for example, 230 V/50 Hz or 120 V/60 Hz), held within the tight tolerances defined by IEC 62087. Power is measured with a high-accuracy power analyzer meeting the low-power measurement requirements of IEC 62301, and luminance is measured with a calibrated photometer or luminance meter whose spectral response matches the photopic V(λ) curve, with all instruments traceably calibrated.
Sample Preparation and Stabilization
The unit is restored to factory default settings, connected at its native resolution and refresh rate, and all automatic power-down, screen-dimming, and eco features are configured exactly as required by the referenced test method. The display is energized and allowed to warm up until readings stabilize, typically 30 to 60 minutes, before formal data collection begins.
On-Mode Power Measurement
For televisions and video-capable displays, on-mode power is measured while looping the IEC 62087 dynamic broadcast-content video signal. For computer monitors, the specified static or slowly updating test patterns are used according to the referenced method. Power is averaged over a minimum measurement interval (commonly at least 10 minutes) after stabilization. Concurrently, luminance is measured at the defined screen positions to compute average luminance, luminance uniformity, and luminous efficacy.
Sleep, Off, and Standby Mode Measurement
Sleep mode is triggered through the standard signaling method, such as a DPMS sleep command from the source device, and power is recorded after the reading has stabilized. Off mode is measured with the unit switched off but remaining connected to the mains. All low-power measurements follow IEC 62301 procedures, and networked standby is evaluated for products with always-on network functions.
Calculation of Efficiency Metrics
The measured on-mode power is used to derive program-specific metrics: EEI is calculated as the ratio of measured on-mode power to a reference power that is a linear function of the visible screen area; TEC is computed by weighting the power of each operating mode by assumed daily usage profiles; and luminous efficacy divides the total luminous output (luminance multiplied by screen area) by on-mode power. Results are compared with the applicable thresholds to assign an efficiency grade or label class and to confirm compliance with minimum allowable values.
Quality Assurance and Uncertainty
Testing is performed by ISO/IEC 17025 accredited third-party laboratories with documented uncertainty budgets covering power, luminance, and derived efficiency calculations. Measurement uncertainty is reported alongside results and is taken into account when judging compliance near regulatory limit values.
Applications
Display energy efficiency test reports directly support market access, regulatory compliance, and product optimization objectives:
- China Energy Label registration and determination of the energy efficiency grade for computer monitors under GB 21520.
- EU EPREL energy label registration and demonstration of ecodesign compliance under Regulation (EU) 2019/2021.
- ENERGY STAR certification and product listing for the North American and other participating markets.
- California Title 20 compliance for monitors and commercial displays sold in California.
- Research and development support for backlight design, power supply efficiency, and firmware power management optimization.
- Green procurement documentation, corporate sustainability reporting, and carbon footprint baselining.
FAQ
Which standard applies to my monitor for the Chinese market?
Computer monitors sold in China must comply with GB 21520-2015, which sets minimum energy efficiency and sleep-mode power limits and defines the three-tier energy efficiency grade system used on the mandatory China Energy Label. Flat panel televisions are covered by the GB 24850 series.
How many samples are required for testing?
Most certification schemes require one to three production-representative units per model. Additional units or configurations may be needed when testing a model family or when automatic brightness control verification is required.
How long does display energy efficiency testing take?
Standard testing for a single model is typically completed within five to ten working days after sample receipt, depending on the number of modes, configurations, and target regulations. Multi-standard test programs sharing common measurements can reduce the overall timeline.
What is the difference between TEC and EEI?
TEC (Typical Energy Consumption) expresses expected annual or daily energy use in kWh, weighting each operating mode by an assumed usage profile, and is used by programs such as ENERGY STAR. EEI (Energy Efficiency Index) is a dimensionless ratio of measured on-mode power to a screen-area-based reference power and is the basis of EU ecodesign compliance and the A to G energy label classes.
How is Automatic Brightness Control handled during testing?
If the product ships with ABC enabled, the test method specifies defined ambient illumination conditions at the sensor, and luminance reduction and power are measured under those conditions to determine whether the feature qualifies for any allowance. In many schemes, ABC can also be disabled if it does not provide the required luminance reduction.
Can one test report cover multiple similar models?
Yes, where models differ only in features that do not affect power consumption, representative unit testing may cover the family, subject to the specific similarity rules of each regulation or certification program. The laboratory evaluates platform equivalence before extending results to additional model numbers.