Office of Environmental and Energy Coordination

Fairfax County, Virginia

CONTACT INFORMATION: Our office is open to visitors by appointment only. Please call or email from 8:30 a.m. - 5:00 p.m., Monday through Friday.

TTY 711

12000 Government Center Pkwy, Suite 533
Fairfax, VA 22035

John Morrill,
Acting Director

What is an LED?

Step into the lightbulb aisle at any grocery, hardware or home good store and you will find dozens of options. Everything from large fluorescent tubes to mini incandescents for flashlights is on display, challenging you to choose the best possible bulb for your needs.

Maybe you’ve heard about LEDs, or light-emitting diodes, and that they’re more efficient and therefore better for your wallet and the world, but what makes them so special? What is an LED, anyway?

To understand why LEDs are preferable to other types of bulbs, and what makes them so efficient, let’s explore all of the options.

Incandescent bulb image courtesy of Johanes PlenioIncandescent bulbs arrived on the scene in 1879, courtesy of Thomas Edison. These bulbs produce light from heat. Inside the glass casing of the bulb lies a metal filament that is heated by the electric current that passes through it when you flick the light switch. As the filament heats up, it glows and produces visible light. Importantly, 90% of the electricity used by an incandescent bulb is given off as heat. Only 10% of the electricity you pump into a bulb is used to produce light – very inefficient, by any standard.

Compact fluorescent bulbCompact fluorescent lightbulbs, or CFLs, are a common alternative to incandescents. The well-known spiral CFL was invented in 1976 by Edward Hammer, who worked for General Electric. These bulbs rely on an interaction between electric current and the elements argon and mercury, which are contained in the bulb as a vapor. As the electricity is driven through the vapor, invisible ultraviolet light is generated, which in turn agitates a fluorescent coating on the inside of the bulb, creating visible light. Far better than their incandescent cousins, CFLs convert 85% of the energy you pump into them into visible light, but the mercury inside makes them a bit harder to dispose of safely.

Changing a lightbulb to an LEDLEDs capable of producing visible light were first invented in 1962 by Nick Holonyack, another General Electric engineer. Each LED bulb contains one or more semiconductors, or material that sometimes acts as a conductor, and sometimes acts as an insulator of electricity. Each semiconductor is made up of a positively charged anode and a negatively charged cathode, elements that conduct electrons. The cathode has an abundance of electrons floating freely, while the anode has “holes” electrons could fall through. When an electrical current is applied, electrons move from the cathode to the anode and some of them fall through the “holes,” colliding with positive particles and losing some of their negative charge. As this change occurs, energy is released in the form of photons, or light.

This sounds complicated, but the takeaway is simple: through this process, LED lightbulbs convert 90% of the electricity you’re paying for into light, making them extremely efficient and a cost-effective option for your home. For more information, check out our LED lighting guide.

Next time you find yourself staring down a wall of bulbs, reach for the LED to save both money and energy.

Fairfax Virtual Assistant