How LED Light Bulbs Work

LED lights
LED lights come in a variety of shapes and sizes. Pierre Longnus/Getty Images

The light bulb that has lit up our homes since the 1800s was officially on its way out after former President George W. Bush signed the Energy Independence and Security Act of 2007. Although the act didn't ban the use, purchase, sale or manufacture of incandescent bulbs, it did require household light bulbs to have 25 percent greater efficiency (which means 25 percent less energy use) than the traditional bulbs that used between 40 and 100 watts of electricity. The inefficient incandescent, where 90 percent of its energy is given off as heat, had fallen out of favor with the financially and ecologically concerned.

When the new lighting standards began in 2012, prime replacements for the incandescent light bulb were the higher-efficiency compact fluorescent lamps (CFL) and the light emitting diodes (LEDs). The CFL, though, has its own problems, primarily the inclusion of toxic mercury in the design and a strange, sometimes unpleasant color that even gives some people headaches.


Enter the LED lights. LEDs have been around for many years — they light up digital clocks, Christmas lights, flashlights, traffic signals, etc. But as far as household lighting goes, LEDs weren't taking off. Certain drawbacks had kept companies from manufacturing them in standard, replacement-size light bulb form. But in the last decade or so, these LED replacement bulbs, the kind you just screw into a lamp like you do an incandescent bulb, have become much more common — which is to say a large number of businesses and households are using them.

A 2017 survey showed that 70 percent of Americans had bought at least one LED light bulb and 38 percent had switched over from incandescent bulbs to LEDs. This percentage has likely increased since 2017.

In this article, we'll look into how LED light bulbs work, why they're a desirable lighting choice, and some of the pros and cons surrounding them. Let's begin with the basics: How does an LED produce light?


LED Light Bulb Basics

An LED is what's called a "solid-state lighting" technology, or SSL. Basically, instead of emitting light from a vacuum (as in an incandescent bulb) or a gas (as in a CFL), an SSL emits light from a piece of solid matter. In the case of a traditional LED, that piece of matter is a semiconductor.

Stated very simply, an LED produces light when an electrical current passes through a microchip, which illuminates the tiny light sources called LEDs and the result is visible light. For a complete explanation, see How Light Emitting Diodes Work.


The problem with LEDs as primary home lighting was that while they emit a lot of light, the structure of an LED caused some of that light to get trapped inside. So, an LED bulb was traditionally dimmer than an incandescent bulb, and most people want their lamps and ceiling fixtures to be pretty bright.

Now, LEDs bulbs have brightened up. You can now find LED replacement bulbs that emit light equivalent to a 60-watt incandescent light bulb or higher, which makes them a viable technology for basic lighting needs at home. And a LED replacement light bulb has a life 24,000 hours longer than that of a traditional incandescent 60-watt bulb.

And it's cheaper. Replacing your home's five most frequently used light bulbs with LED ENERGY STAR models, can save you $75 a year.

Which brings us to the pros and cons of LED light bulbs.


Advantages of LED Light Bulbs

LED light bulb
LED light bulbs have become very popular now. Yuji Kotani/Getty Images

First, there's the reduced energy use. The LED method of producing light uses far less energy to heat than do other lighting technologies. It's dramatically more efficient than the vacuum/filament method used in incandescent bulbs — using at least 75 percent less energy and it emits very little heat in comparison with incandescent bulbs (which release 90 percent of their energy as heat) and CFLs (which release about 80 percent of their energy as heat).

If you operate your lighting for 4,320 hours per year (360 hours per month/90 hours a week/12.85 hours a day), a 100-watt incandescent bulb would use 432 kilowatt-hours per year, while an equivalent 14-watt LED bulb would use just over 60 kilowatt-hours per year. LEDs also emit 90 percent less CO2 than the old halogens and 50 percent less than CFLs.


But energy efficiency is just part of the story. The other part is time efficiency: A good-quality LED bulb theoretically can have a life span of 25,000 hours or more, while incandescent bulbs have a 1,000-hour life span. Solid-state lights like LEDs are more stable light sources than incandescent or fluorescent bulbs, and the difference is startling: You'd have to leave a LED light on for 24 hours a day, seven days a week for three years before it matches an incandescent bulb's life span. (In fairness, not all LED light bulbs last as long as they can in theory. Some may have shorter life spans if parts wear out prematurely.)

Because of that time benefit, things get a bit more muddled when you get into the cost issue. A 60-watt LED replacement bulb runs in the area of $9.48 for a four-pack, while the same pack cost $3.97 for incandescent bulbs, according to Home Depot.

The reality is, even at $9.48 for a pack of four bulbs, LEDs will end up saving money in the long run, because you only need one every decade or two and you spend less money on home lighting, which can be six to seven times more energy efficient than incandescent lights and cut energy use by more than 80 percent.


Concerns About LED Light Bulbs

LEDs are poised to take over household lighting. Philips has a collection of LED lights that includes color changes and Wi-Fi connected bulbs. And General Electric has a LED+ series that includes light bulbs with speakers, timers, color changes and more. It's estimated that LEDs will account for 75 percent of all lighting sales by 2030.

If you look at what the scientists are saying about LEDs, the picture does look pretty rosy. Breakthroughs are popping up at a breakneck pace. Except there's one problem.


A growing number of studies have come out about the blue light that LEDs emit. Researchers say it may be damaging our eyes and health. A French health agency said it can damage the eye's retina while disturbing our biological rhythm and sleep disruption. The agency recommended limiting the use of LED devices with the highest blue-light content, especially for children. This would include computers, smartphones and other screens, as well as perhaps, certain toys and decorative lights.

The 2019 report confirmed the agency's 2010 results regarding the toxicity of blue light to the eye, which can lead to failing eyesight. "They show short-term phototoxic effects associated with acute exposure and long-term effects associated with chronic exposure, which increase the risk of developing age-related macular degeneration (ARMD)," the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) wrote in its report.

For more information about LED light bulbs and related topics, look over the links on the next page.


LED Light Bulbs FAQs

How LED light bulbs work?
An LED produces light when electrons move around within its semiconductor structure. A semiconductor is made of a positively charged and a negatively charged component. The positive layer has "holes" -- openings for electrons; the negative layer has free electrons floating around in it. When an electric charge strikes the semiconductor, it activates the flow of electrons from the negative to the positive layer. Those excited electrons emit light as they flow into the positively charged holes.
What are the advantages of LED bulbs?
LED bulbs consume less power than other lighting technologies. They are also energy-efficient, safe to use and have a longer life. Compared to incandescent light sources, LED bulbs are 85% more energy efficient.
Can LED lights be left on all the time?
Yes, LED lights are ideal for places where light needs to be left on all the time. You don’t have to worry about high electricity bills because LED bulbs consume low power and generate less heat.
Do LED lights burn out?
Typically, LED lights can last for up to 25,000 hours. However, just like other electronic components, LED lights may burn out before that, due to extreme voltage fluctuations or premature part failures.
Does turning LED lights on and off shorten their life?
No, turning the LED light on and off doesn’t shorten its operating life. This usually happens with fluorescent bulbs. What really shortens the life of LED bulbs is overheating. So, make sure you don’t have electricity fluctuations to prevent overheating the LEDs.