Energy Efficiency | March 25, 2016

LED vs CFL Bulbs: Which is More Energy Efficient?

The wholesale switch from incandescent light bulbs, which were discontinued for wattage above 40 watts in 2014, to the more energy-efficient compact fluorescent lamp (CFL) bulbs and light emitting diode (LED) bulbs has been evolving for years. A lot of confusion still exists, however, about these bulbs, starting with which is which. Is the long light bulb the CFL bulb and the LED the curly light bulb? Or is it the other way around — CFL is the curly light bulb and LED is the long light bulb? And that’s before we even analyze which one is more energy efficient!

In short form, here are the answers: CFL is the curly light bulb and LED is the long light bulb. And, in the CFL vs LED battle for energy efficiency, the LED light benefits make it a winner, hands down. Here’s what you need to know.

CFL vs LED Bulbs

To understand LED light benefits, it’s important to understand the difference between the two bulbs. LED light bulbs produce light when an electrical current passes through them. In CFL bulbs an electric current flows between electrodes at each end of a gas-filled tube. The reaction creates ultraviolet light and heat, which is then changed into light when it hits a phosphor coating on the bulb’s interior. This process takes anywhere from 30 seconds to 3 minutes to complete, according to ENERGY STAR®, which is why it can seem as if your CFL light takes a while to be fully lit.

CFLs used 25-35% less energy than incandescent bulbs, but it you really want to make the biggest environmental impact on the environment, choosing LEDs is the way to go. Residential LEDs, especially those rated by ENERGY STAR, use 75% less energy and last 25 times longer than incandescent lighting. notes that by 2027 widespread use of LEDs could save about 348 TWh of electricity, the equivalent of annual electrical output of 44 electric power plants (1000 megawatts each). It’s also a total savings of more than $30 billion at today’s electricity prices.

Here are some other differences to keep in mind when examining CFL vs LED bulbs:

  • LEDs emit very little heat. In contrast, incandescent bulbs release 90% of their energy as heat, CFLs release about 80% of their energy as heat, according to
  • Another LED light benefit is that LEDs, because they emit light in a specific direction, do not need diffusers or reflectors that trap lights. This helps increase LED efficiency for uses such as downlights (recessed downlights are common in residential kitchens, hallways and bathrooms) or task lighting.
  • The Department of Energy estimates that there are at least 500 million downlights in U.S. homes, with more than 20 million sold each year. The DOE estimates that both CFL and LED lighting could decrease downlight wattage by at least 75%.
  • The same LED string of holiday lights could still be in use 40 holiday seasons from now, according to

This chart shows the difference in costs between CFL vs LED bulbs:

LED vs. CFL: Difference in Costs



The difference between lumens and watts

Something else consumers need to understand while analyzing CFL vs LED bulbs is the difference between lumens and watts. Consumers are used to buying light bulbs based on watts, or how much energy they consume. It didn’t matter how much light (lumens) they provided. Now, as a way to differentiate LED vs CFL bulbs, manufacturers are classifying the new energy-efficient bulbs by their lumens. You are buying your bulb based on the amount of light you want rather than the energy used by the bulb.

Admittedly, it can be confusing. Here’s the basic point to keep in mind: More lumens equals more brightness. But exactly how many lumens is equivalent to what was once, say, a 60-watt bulb? Here’s a breakdown to give you the basic new LED vs CFL light bulb math:

  • To replace a 100-watt incandescent bulb, choose a bulb with about 1600 lumens.
  • To replace a 75W bulb, choose a bulb with about 1100 lumens.
  • To replace a 60W bulb, choose a bulb with about 800 lumens.
  • To replace a 40W bulb, choose a bulb with about 450 lumens.

Difference Between Lumens and Watts



The reality is that while switching light bulbs from CFL to LED can seem like a small step toward energy efficiency, the result nationwide can be a win-win for everyone: potentially lower energy costs in your home and in the U.S. as a whole.

Want to know more about which of your appliances wins the energy efficiency battle? Take our energy efficiency quiz. Then find the rest of our series examining the details of each appliance, starting with  electric vs natural gas dryer.

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Comments ( 10 )

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Peter Bennett - 4/8/2017

The article neglects to mention the price of the bulbs. I found in my local Walmart that 1500 lumen LED (100w equivalent) are around $40 apiece. Over 15 years, this more than doubles the cost shown above. Who knows whether we will still be using the bulb in 15-25 years?

800 lumen (60W equivalent) are $1 each. I am not sure why, but these are certainly cost effective. I suspect they are being subsidized.

    Constellation Community Team - 4/21/2017

    Hello, Peter. Thank you for your comments. Yes, LED bulbs tend to be more expensive than traditional incandescents or CFLs. And, you raise a good point about whether or not we will be using these in ~20 years or if there will be an even better alternative. For now, though, we’re looking solely at the savings with respect to energy use. LEDs definitely use less energy than other kinds of bulbs with equivalent lumens. You might not wish to replace all of your bulbs with LEDs at the same time because of the cost, but we’re hopeful that perhaps people will gradually replace their traditional bulbs with energy-efficient alternatives like LEDs.

    Thank you so much for sharing your thoughts and comments. I really appreciate your input!

Dan - 3/19/2017

The statement about 500 million US homes having downlights must be a mistake. I don’t think that there are even that many people in the US. Good comparisons of lights though. In my experience CFL bulbs never had the the long life that was claimed, I am getting much longer life out of LEDs.

    Constellation Community Team - 3/21/2017

    Dan, thank you! You’re correct. I’ve changed the original post to say that there are 500 million downlights in U.S. homes, but not that there are that number of households. Thanks for the great catch! 🙂

    I’m glad to hear that you’re finding success with your LED bulbs, and thank you for making energy efficiency a priority!

Brihat Energy - 3/10/2017

Very informative blog.! LED lighting has more benefits that traditional Bulbs. Some of benefits are Long life , energy saving this helps in reducing electrical bills, durable, Ecologically Friendly, Zero UV Emissions.

    Constellation Community Team - 3/20/2017

    Thank you for sharing your thoughts! Yes, I agree that there are lots of benefits to LED lights, and I am so glad that it sounds like you’re thinking of using them. Be sure to check back on the blog often, because we’re always sharing additional tips and ideas for how you can save energy.

Michael Wingo - 2/28/2017

From my experience, the CFL bulbs save about 76% over incandescent while the newer LED bulbs save about 87% over incandescent. In comparing LED to CFL, the newer LED save approximately 42% over CFL. Older LED bulbs are generally not as efficient as the newest ones. Also, the LED bulbs I am familiar with are not long, but formed into the same shape as an incandescent bulb containing multiple, and tiny LED’s.

    Constellation Community Team - 3/3/2017

    Hi, Michael. I appreciate your taking the time to share your thoughts and insights. As technology changes and newer products hit the market, the specifics on the efficiencies of one type of bulb over another is bound to change, as well. However, I am so glad that you’re making the effort to find and use the most energy-efficient bulbs. Please check back with us for more information — we’re always working to provide insights into ways that people can be energy-efficient in all aspects of their home and business!

Darwin Crew - 8/11/2016

There is excellent information on this site and a lot of good comparisons between LED and CFL.

    Constellation Community Team - 3/3/2017

    Thank you for taking the time to comment. I am so glad that the information has been helpful to you. Please do check back on the blog again soon for more tips on how to manage energy use in your home or business. Thanks!

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