40W Bulbs

We tested thirteen brands of 40W GLS bulbs as per the specifications set by the Bureau of Indian Standards (BIS).



January – February 2007

40W Bulbs

  • We tested thirteen brands of 40W GLS bulbs as per the specifications set by the Bureau of Indian Standards (BIS).


  • The markings on all the samples of Wipro Safelite came off the glass surface even on normal handling. Thus they did not satisfy the requirement of ‘legible’ and ‘indelible’ marking as per the Standard. In the case of Orient, the glass bulb was marked with 40W and its wrappers had mark of 25W, 215 lumen which should have been 40W 410 lumen.

Minimum Life

  • As against the Standard requirement of minimum 960 hours of average life, Prakash Lites and Wipro Safelite had a life of only 776.37 hours and 941.04 hours respectively.

Life Test

  • Laxman Sylvania and Crompton were the toppers in the life test with 1179.16 hours and 1177.57 hours. Other conforming brands had an average life between 960 hours and 1124 hours.

Initial Wattage

  • Not a single sample (out of 25) of Diamond passed the initial wattage test. The average initial wattage of Diamond was 44.21W. The Standard limits the maximum initial wattage of individual sample to 42.1W and allows 4 failures. Initial wattage is found to be the lowest in Philips (40.12W) and the highest in Laxman Sylvania (41.23W) among the conforming brands.

Initial Lumen

  • The initial lumen i.e. light output measured initially of a 40W 230V bulb should not be less than 385.95. GE Classictone Clear had the highest average initial lumen at 454.55 followed by New Cema Super at 450.56. Our topper – Crompton had the average lumen at 416.98.

Lumen Maintenance

  • BIS has specified test for lumen maintenance at 750 + 25 hours. It should not be less than 85% of the initial lumen of the individual lamp. Among conforming brands, the lumen maintenance was the highest in Crompton at 95.36% and the lowest in Laxman Sylvania at 91.70%.
  • The Standard does not prescribe test for lumen maintenance after 1250 hours but we tested it for consumers’ benefit. Crompton maintained 92.75% average lumen (highest) and Laxman Sylvania had the lowest lumen maintenance at 89.47%.


  • The efficacy at 1250 hours was tested in the interest of consumers. Bajaj gave the highest efficacy with 10.42 and Laxman Sylvania had the lowest at 8.79. This is a test not specified under Indian Standard. The higher the efficacy, the better the utility of the bulb.

Extended Life Test

  • Those bulbs surviving till 1250 hours were subjected to an extended life test. Out of a sample of 20 taken as per BIS specifications, 14 samples of Crompton and 11 samples each of Laxman Sylvania and Surya Super were available for the extended life test. Laxman Sylvania had total average life of 1337.65 hours followed by Crompton (1330.26 hours). Bajaj had the lowest average life of 965.95 hours. Other conforming brands have total average life between 965 and 1233 hours.

Energy Cost

  • Laxman Sylvania makes you incur the maximum energy cost of Rs.963.13 per year and Philips Classictone Clear helps you incur the lowest at Rs.937.20.





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