5 Factors to Consider when buying an Energy Efficient Light Bulb

Making the switch from incandescent light bulbs to energy efficient compact fluorescent or LED bulbs can be a great process. Not only will you immediately start saving energy, but you'll be saving money as well. In addition, you can wave goodbye to the days of burning your hands when trying to change a bulb. Speaking of which, energy saving light bulbs last so long, changing them often will become a thing of the past. Before you jump head first into this switch, here are 5 very important factors that need to be considered when you're choosing the right bulbs for your needs.


Wattage is a measurement of the amount of energy consumed by the light bulb. In CFLs and LEDs this amount is 75 percent to 85 percent less than the amount of energy consumed by an incandescent or halogen equivalent. For example, a 13-watt CFL can emit the same quality of light that a 60-watt incandescent bulb does. Again, wattage lets us know how much power is being consumed. It does not determine the amount of light that a bulb produces. This is determined by the light output.


The light output of a lamp is measured in lumens. The higher the lumen rating is for a bulb, the brighter a light the bulbs produce. This is how a 13-watt CFL can replace a 60-watt incandescent, while at the same time an LED bulb that uses only 5 watts of energy can replace a 60-watt as well. This is one of the most important factors to consider when choosing a replacement bulb.


At the very bottom of the bulb, you have the base. Its shape and type determines whether or not the bulb will be able to plug into a specific fixture. The specific base type can be found inscribed onto the bulb, or on the fixture the bulb goes into. The most widely used bases are:

  • E26 - This is the medium, or standard, screw in base that is used in the majority of fixtures.
  • E12 - Smaller than the medium base, and often referred to as a candelabra base, lights of this type are used in most decorative fixtures, such as chandeliers.
  • E39 - Known as the mogul base, this one also screws into a fixture, but is larger than both the candle and standard base.
  • GU24 – Bulbs with this base twist and lock into a GU24 fixture. These bulbs can work in any fixture with a GU24 socket.
  • Pin base – Unlike the GU24 bulbs, many pin base bulbs are manufacturer-specific, meaning they often times cannot be placed into a fixture that has the same corresponding base. For example, a fixture from Company A with a GX24q-2 socket may be designed to work only with Company A bulbs, so a bulb with a GX24q-2 base from Company B would not operate properly in the Company A fixture, and may even cause the fixture to short circuit. For pin base bulbs, it’s recommended to stick with the specific model that is being replaced, or checking with the manufacturer before getting a bulb from a different maker.

Color Temperature

With the exception of colored bulbs (red, blue, green, etc.), compact fluorescent lights and LED lights have a color temperature rating. Measured in degrees Kelvin, this tells us how the color produced by the bulb looks in respect to the color of the sun. Beginning with 2700K, the higher the color temperature is, the whiter in color a bulb is. The lower the color temperature, the more yellow the light will appear:

  • 2700K - This is the warmest, or most yellow, the bulbs are available in. Lights with this color temperature are generally used in living rooms or bedroom areas.
  • 3500K - Appearing soft white in color, bulbs with a 3500K color rating are standard for bathrooms or kitchens.
  • 4100K - Cool white in color, these light bulbs are fluorescent white in appearance. They are used oftentimes in hospitals.
  • 5000K+ - These bulbs are on the higher end of the spectrum. Light bulbs with this color temperature are referred to as daylight bulbs, because the light they emit is closest to the appearance of the sun at noon. *With LEDs, 5000K is cool white, with daylight beginning at the 6000K color temperature.


MOL is an acronym for maximum overall length. This is the measurement (either provided in inches or centimeters) of the bulb from the tip of the bulb to the bottom of the base.

There you have it! Keep these 5 factors in mind and you'll spend less time worrying about returning those wrong bulbs, and more time enjoying the extra money you'll be saving on energy bills.

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