Light Bulb Terminology - Ravinia Plumbing
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Light Bulb Terminology

Light Bulb Terminology

When you need to change a light bulb (which should not be as frequently if you are using longer-life bulbs, but that’s another topic), you’ve undoubtedly noticed the specs on the package. Here is a quick explanation of them, in no particular order:

  • Light appearance/light color) is often measured by color temperature, expressed as Kelvin values (K). The warmer the light the lower the temperature.  Warm yellow or soft white lights have a temperature of about 2,700K, while a very bright white-blue or daylight light could be more than 5,000K.
  • Brightness is expressed in lumens (lm).  The more lumens, the brighter the bulb.  Here is a conversion table using incandescent bulbs:
    • 375 lm/25 watts
    • 600 lm/40 watts
    • 900 lm/60W
    • 1125 lm/75 watts
  • Energy use/cost tells us how much energy a bulb uses, expressed as watts. More efficient bulbs such as LED bulbs will tell you how much wattage they use, as well as the equivalent wattage of an incandescent bulb.  For example, a 10-watt LED bulb would generate the same brightness of a 60-watt incandescent.

    Some packages will project an estimated yearly energy cost, and even potential savings compared to less-efficient bulbs.  It will include assumptions on usage and utility rates.

  • Expected life. Many labels will include the expected life of the bulb.  Older bulb labels will have them expressed in hours, more energy-efficient bulb labels will have them expressed in years, based on assumed usage.

  • Energy Star rating. Energy-efficient bulbs such as LED bulbs may carry an Energy Star rating that could allow you to earn rebates from your utility company.


  • If lights are dimmable, that may be indicated.


  • Mercury-free. All LED lights are mercury-free.  CFL bulbs and fluorescent lamps may contain mercury, making them harder to dispose. 

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Ravinia Plumbing, Sewer, Heating & Electric
575 Bond St,
Lincolnshire, IL 60069
P: (847) 579-5565
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