Light bulbs come with their own secret language: E26, GU10, CRI, lumens, Kelvin. Nobody hands you the decoder ring. So here it is. These are the questions we get asked most, answered plainly by the GoodBulb Lumen Masters.
(A quick one to warm up: why did the light bulb fail the test? It kept going out.)
LED basics
What does LED stand for? Light Emitting Diode.
How is an LED different from an incandescent? An LED makes light by passing current through a semiconductor. An incandescent heats a filament until it glows. The LED uses far less energy and lasts far longer.
Can I use an LED in any fixture? Usually yes. Just check the bulb's size, shape, base, and that it fits the fixture's wattage and any dimmer.
Do LEDs get hot? They make some heat, but far less than an incandescent, and a good bulb pulls that heat away through a heat sink so it stays cool to the touch.
Performance and efficiency
How long do LEDs last? A quality LED runs 25,000 to 50,000 hours. Watch out: many big-box LEDs are built to last only 8,000 to 10,000, the same planned-obsolescence trick in a new package.
Are LEDs energy efficient? Very. A good LED uses about 90% less energy than the incandescent it replaces.
Do LEDs save money? Yes, on both your power bill and on replacements you no longer have to buy.
Color and light quality
What is CRI? Color Rendering Index measures how true colors look under a light, on a scale of 0 to 100 compared to sunlight. Higher is better; look for 90+.
Can LEDs be dimmed? Many can. Check that the bulb is labeled dimmable and pair it with an LED-compatible dimmer.
What is color temperature? Measured in Kelvin (K), it is the hue of the light. 2700K–3000K is warm and yellowish, 4000K is neutral, 5000K is crisp daylight.
Safety and environment
Are LEDs safe? Yes. No mercury (unlike CFLs) and very little heat, so less risk of burns or fire.
Are LEDs eco-friendly? Yes. Less energy and far fewer replacements mean less waste and a smaller footprint.
Can I use LEDs outdoors? Yes, if the bulb is rated for outdoor use and weather.
Can bulbs be recycled? Yes, and it matters. CFLs and fluorescents contain mercury and should never go in the trash. GoodBulb has a recycling program to help you retire old bulbs the right way.
See GoodBulb recycling →
The technical stuff
What are lumens? The amount of visible light a bulb puts out. More lumens, brighter light. Shop by lumens, not watts.
What is an LED driver? The small electronics that regulate power to the LED. A good driver keeps the light steady and flicker-free; a cheap one is where bargain bulbs fail.
Why do some LEDs flicker when dimmed? Usually a mismatch between the bulb and the dimmer. An LED-rated dimmer fixes it.
How is a bulb's "hour rating" set? It is the average rated life. Makers test a large batch and record the hour at which half have burned out. Some last longer, some shorter.
How do you measure a bulb's length? End to end, including the base. That figure is the Maximum Overall Length (M.O.L.).
120V vs. 130V? U.S. line voltage is 120V. A 130V bulb can last longer and better survive surges, but runs about 15% dimmer.
What is 277V–480V? High-voltage systems used in commercial and industrial buildings.
How do I know what wattage to use? Check the fixture's rating. The wrong bulb can burn out early or become a fire hazard.
What is an ANSI code? A standardized designation from the American National Standards Institute (for example, E26 = standard medium screw base).
A few more
Do LEDs emit UV? Most lighting LEDs emit little to no UV. (There are special UV LEDs made on purpose for other uses.)
Is switching to LED easy? Yes. LED bulbs are built to fit standard fixtures, so most swaps are one-for-one.
Do LEDs attract bugs? Fewer than incandescents, because they give off less heat and UV.
Can I toss LEDs in the trash? They have no mercury, but recycling is the better choice. Ask us, or use our recycling program.
Still stuck?
That is what we are here for. Ask a Lumen Master →
And when you replace a bulb, a GoodBulb LED, made in America and built for 25,000 hours, means one less question next time.
