In the light bulb industry, the Average Rated Life of any light bulb is defined by how long it takes for a percentage of the light bulbs in a test batch to fail. For instance, if 100,000 bulbs were tested and after 1000 hours, 70,000 (70%) of the bulbs had expired. This product would have an average rated life of 1000 hours at L70. There will of course have been many failures during the initial 1000 hours and likewise there would have been a number of lamps lasting well in excess of 1000 hours.

The two important factors when understanding the life expectancy of your chosen light bulb are the Hours and the L rating stated. Examples below:

[infobox title=’Understanding Life Time Hours’]2,000 hours at L50 indicates that 50% of Light bulbs had failed at 2,000 hours.

5,000 hours at L70 indicates that 70% of Light bulbs had failed at 5,000 hours.

12,000 hours at L80 indicates that 80% of Light bulbs had failed at 12,000 hours.

20,000 hours at L95 indicates that 95% of Light bulbs had failed at 20,000 hours.[/infobox]

It is an extremely simple but very important factor in understanding the expected life of any light bulb purchased.

Another important aspect to take into consideration is that all light bulb ratings are carried out under perfect laboratory conditions. There are numerous other factors that will determine the life of any light bulb. Electrical surges, extreme cold, vibration and extreme heat are just a few examples of instances where the Life time of the product will be affected. Any number of factors could determine the performance and ultimately the life of a light bulb.