Lamp Life

Lamp life, also referred to as rated life, is the time in hours a lamp will last before a percentage of lamps will burn out.  The exact definition of lamp life, as well as the testing criteria varies between light sources, make comparisons of lamp life between light sources difficult. For example, the rated life for incandescent and fluorescent lamps is 50% failure — which means in a room of 10 identical fluorescent lamps in identical conditions, the rated life of that lamp is the time it takes for 5 of those lamps to burn out.  LED light sources, however, are typically measured by “L70” rating.  This rating is the time it takes for the LED source to reach 70% of the initial light output, or a 30% reduction in output.

In spite of these challenges, we can still effectively compare the rated life of various light sources.  Modern LED light sources are designed to last longer than conventional light sources as noted here:

Lamp LifeCurrent LED lighting sources far exceed the life expectancy of all traditional light sources.  An LED source with a lamp life of 100,000 hours could be kept on for 11 years continuously before the light levels depreciate to the point of needing to be replaced.  For applications that do not require lighting 24/7, such as a parking lot or interior office, the life extends to 20+ years.

Lamp Life = $

Longer lamp life means lower maintenance costs.  Without failing lamps, the time needed by an employee to physically replace the lamp is eliminated.  In areas where lamps are not easily accessible –gyms, parking lots, auditoriums, etc. — the cost of renting or purchasing expensive lift equipment or building scaffolding is also eliminated.  The need to store boxes of replacement lamps is gone, not to mention the savings of the cost of the lamps themselves.

On the flip side, LED lamps are not easy to replace. Incandescent, fluorescent, and even HID lamps are relatively easy to unscrew and replace.  LED lighting boards are typically more difficult, and can be impossible to replace.  The alternative to replacing an LED lamp is purchasing an entirely new fixture.  The replacement of LED lamps is a known issue, and is currently being addressed by LED lighting manufacturers.  Interestingly, many manufacturers believe when today’s LED fixtures need to be replaced in 20 years they will have new, even better and more efficient technology to replace the failed LED fixture.  Most manufacturers, however, are currently trending toward making their LED boards easily “swappable” for new LED boards.

Factors That Effect Lamp Life

There are several factors that will adversely affect the lamp life of a light source:

  • a hot environment
  • vibrations from machinery or slamming doors
  • exposure to water or moisture
  • cycling the lamp on and off

Different light sources react differently to these variables. While heat has an adverse effect on most light sources a cold environment generally has a positive effect on LED lamp life.  Incandescent, fluorescent, and HID lamps are very sensitive to vibrations, whereas LED have proven to be much more durable.  Cycling (turning on and off) lamps can have an adverse effect on the overall lamp life of fluorescent sources. In fact, florescent lamp life is measured based on a 3 hours on/20 minutes off cycle. LED and incandescent lighting are not effected by cycling —  LED lamps can even be used as a strobe without an appreciable change in lamp life.

This exploration of Lamp Life
is written and illustrated
by Chad Greiner, LC, CTS-D
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Chad A. Greiner, LC, CTS-D is looking forward to talking with you about your lighting needs and challenges. You can reach him at our office by dialing 419-824-2400.