With incandescent bulbs, lighting magic happens before your eyes: Electricity heats the metal filament until it becomes hot, producing light. But with LEDs, technology and sophisticated engineering are carefully packed into the lightbulb.

Inside an LED Bulb
The interior of an LED bulb reveals a digital revolution up close, according to John Banta, the engineer who oversees Consumer Reports’ lightbulb tests. Electricity passes through semiconductor material, sparking up light-emitting diodes, while a heat sink absorbs and releases the small amount of heat produced. Unlike with incandescents, most of the energy used by an LED creates light. (Ninety percent of the energy used by incandescent bulbs escapes as heat.)

While LEDs do not get hot the way incandescents bulbs do, their heat must be drawn away. Known as thermal management, it’s probably the most important factor for an LED to perform well over its lifetime, according to Energy Star. Otherwise, the light fades faster, so the bulb won’t be bright enough to use for as long as the manufacturer claims.

Shifting Shapes
LED bulbs come in various shapes as manufacturers work to improve efficiency and light distribution, help manage heat, and lower costs. Among LEDs that are bright enough to replace 60-watt incandescents, the Feit Electric LED is shaped like an incandescent and surrounded by fins that help prevent heat buildup. The Philips SlimStyle is a flat bulb that doesn’t need a heavy heat sink, so it weighs less. Both LEDs are CR Best Buys and cost $7.

One of the more unusual-looking bulbs we've tested is the Nanoleaf One. A tangle of vines cover this odd-shaped LED, along with uncovered yellow diodes that aim to provide more light. It costs $35 and was the least impressive of the 75-watt-equivalent bulbs in our Ratings.

Inside an LED lightbulb.

Choose the Right Bright Light
Our Lightbulb Buying Guide will enlighten you on the different types of bulbs you can buy.

Pros and Cons of LEDs

LEDs do not burn out like other bulbs do. Instead, they fade over time, and when the light has decreased by 30 percent it’s no longer considered useful. (Manufacturers' claimed life is a prediction of when the 30 percent decrease will happen.)

LED Advantages 

  • Use about 80 percent less electricity while providing the same brightness of the incandescents they replace.
  • Use slightly less energy than CFLs.
  • Brighten instantly.
  • Lifespan not shorted by turning them on and off frequently.
  • Some dim as low as incandescents do.
  • Most claimed to last 20,000 to 50,000 hours when used three hours a day (about 18 to 46 years).

LED Disadvantages

  • Typically cost more than other bulbs.
  • Not all A-type bulbs (the kind used in lamps and other general-lighting fixtures) are good at casting light in all directions.
  • Most are good but not great at accurately displaying the colors of objects and skin tones.
  • Some are bigger or heavier than other bulb types.

We've tested dozens of LEDs and CFLs. Before you spend a dime, check our lightbulb Ratings to find the brightest energy-saving bulbs. Be sure to check for utility rebates before you shop, and note that Energy Star-qualified LEDs have a warranty of three years or longer.

Any questions? Send them to me at kjaneway@consumer.org.