CLASP Analysis of Background Illuminance Levels During Television Viewing

Publication Date: 
12/01/2011

Televisions account for a growing portion of residential energy use worldwide. In the U.S. alone, TVs consume approximately 50 billion kWh of energy each year. Energy efficiency standards and labeling (S&L) programs, including the EPA’s ENERGY STAR program, have saved significant energy; now the Department of Energy is developing a federal test procedure to measure the energy efficiency of various television sets. 

In support of these efforts, CLTC partnered with the Collaborative Labeling & Appliance Standards Program (CLASP) to conduct a field study of typical background lighting levels during in-home TV viewing. Data collected through the study—based on a diverse sample of 60 homes, 30 in Sacramento and 30 in the Washington, D.C. area—will enable ENERGY STAR, the DOE, and other regulatory entities to measure the energy consumption of TVs when the automatic brightness control (ABC) feature is engaged in a way that more accurately reflects actual use.

Methodology

In October of 2011 CLTC staff members installed equipment in 30 participating homes throughout the Sacramento area and 30 homes in the Washington, D.C. area. An illuminance meter and a power meter were installed on each TV monitored for the study, the illuminance meter placed near the center of the bottom bezel to closely match the location of television illuminance sensors. Data were collected over a seven-day period.

In the course of installing equipment, CLTC staff took photos and made sketches of the TV viewing rooms, with windows, lamps and other light sources noted on the sketches and later incorporated in room illuminance profiles.

Shugoll Research developed screening criteria and selected a diverse sample of homes for the study, in order to obtain a broad range of lighting conditions and to reflect a broad demographic mix (in terms of household sizes and housing types, ages, income levels, etc.).

Keith Jones, from Australian Digital Testing, joined CLASP staff and CLTC staff members Konstantinos Papamichael and Kyle Sills to analyze the data and identify essential findings.

Findings

  • Typical daytime room illuminance levels can be characterized by three illuminance profiles

  • Typical nighttime room illuminance levels can be categorized into two illuminance profiles

  • Very little television viewing occurs at background lighting levels of 0 Lux

  • The majority of television viewing (89%) occurs between 0 and 100 Lux (including both daytime and nighttime viewing)

  • The consistency between results for the majority of houses sampled suggests that the results may be representative of houses in the Northeastern and Northwestern regions of the United States

Conclusions & Recommendations

  • The 0 Lux and 300 Lux test points specified in the ENERGY STAR test procedure should not be used to measure television energy consumption with the automatic brightness control (ABC) feature enabled
  • Three test points—between 10 Lux and 100 Lux—should be used to measure television energy consumption
  • Further analysis is needed to determine if differences in the length of TV viewing periods during the day, versus at night, impacts television energy consumption
  • Further data collection is recommended, including in regions outside of the United States

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