Output, shape, color temperature, and Energy Star rating are factors to consider when buying a light bulb.

Photograph by Sideways Design/Shutterstock

Updated by James Robertson

for National Geographic

What to Look For

Although there are other options, including LEDs and halogen bulbs, when it comes to cost, availability, and savings, compact fluorescent bulbs (CFLs) still offer the best value for lighting. You can now find LEDs for around $20, while CFLs average from $2-$10.

  • Lumen output: To maximize energy savings, choose the product that provides the most lumens at the lowest wattage. Energy Star lists common lumen equivalencies for CFL and incandescent wattages.

  • Shape:

    • Triple-tube bulbs provide high light output in small spaces, ideal for desk and reading lamps.
    • Flood lamp CFLs work well for recessed and track lighting.
    • Globe shapes work well in bathrooms and above vanity mirrors where aesthetics are important.
    • Torpedo-shaped candelabra bulbs fit nicely in small light fixtures such as sconces and designer lamps.
    • Dome-shaped CFLs, similar in look to conventional incandescents, are a better fit for lamps whose shades clip onto the bulb.
  • Kelvins: A CFL’s color is indicated by the Kelvin (K) temperature (listed on the package). Higher Kelvins, 5000K or 6000K, correspond with cooler, bluer colors, while lower Kelvins, 2700K or 3000K, give off a warm, cozy glow similar to incandescents. If the package doesn’t list the Kelvin temperature, look for descriptive phrases like “warm white” and “soft white.”

  • Energy Star rated: Energy Star CFLs use 75 percent less energy than standard incandescent bulbs.

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