Light Bulbs 101
When you think of light bulbs, you probably think of one with a brass-colored screw-in base and bulbous white glass. While that’s definitely not the only kind of light bulb out there, it is one of the most well-known!
In this guide, we’ll take a closer look at the types of bulbs and some common sizes of bulbs. Don’t worry, there won’t be a pop quiz at the end. But, once you’ve read this guide, we hope that you’ll know a lot more about light bulbs.
You can also shop our selection of bulbs.
Types of Bulbs
Incandescent: This is the bulb you think of when you think of light bulbs. And no, incandescent bulbs haven’t disappeared from the market! You can still find them at department stores, hardware stores or anywhere else you buy bulbs.
In fact, incandescent lighting has experienced a surge in popularity thanks to the Edison bulb trend. Edison bulbs, named after Thomas Edison (the inventor of the incandescent light), often feature intricate designs in the filament.
Incandescent light bulbs tend to give off a yellowish glow, which is called warm white light. You may prefer this kind of light based on familiarity with it, or based on a certain mood you would like to create with your lighting, and that is OK!
Incandescent bulbs have become more energy-efficient in recent years, due in great part to government regulations. They now use fewer watts of energy to deliver the same brightness of light. By the way, that brightness is measured in lumens--the more lumens there are, the brighter the light will be. Learn more about lumens.
Halogen: Halogen lights are actually incandescent lights, but they are slightly different from a typical incandescent. Here's an example of a halogen bulb.
Photo from Shutterstock
Halogen bulbs contain a special gas that helps keep the bulb clean, slightly improving its efficiency. These bulbs tend to burn hotter than conventional incandescent bulbs and cannot be hung facing downward in a bath bar fixture due to the heat.
If you're handling halogen bulbs, it is best to wear gloves or use a cloth to cover your hand. That's because your skin has oils that can contaminate the lining of the bulb. That causes a weak spot and, when that weak spot gets heated, the bulb could burn out or even explode! If you accidentally do touch a halogen bulb with bare hands, gently cleanse the area with rubbing alcohol.
Fluorescent: Most often seen as compact fluorescent lights (CFLs)—you know, those bulbs that have a curly look.
Photo from Shutterstock
Getting scientific for a moment, fluorescent lighting is produced when an electric arc excites the gas in a glass tube, which causes the phosphor coating of the bulb to glow. This process is assisted by a small amount of mercury, which is about 4 milligrams per bulb in the case of CFLs.
Fluorescent light tends to look different from incandescent. This is because fluorescent sources often have a higher color temperature, which means that their light does not have that same yellowish glow that comes from incandescent sources. It can look whiter or even bluish-white.
The advantages of fluorescent light include a longer lifespan and a higher lumens per wattage output (more brightness with less energy used). The downsides include the fact that they must be disposed of in a special way (you can't just put them in your household trash!) and can be dangerous if they break because of the mercury.
You may want to try using fluorescent bulbs in fixtures that aren’t used very often--closets, attics, garages or laundry rooms, for example. They last longer than incandescent bulbs, so they won’t burn out as quickly!
LED: Let’s get scientific again to explain what makes LED lights different from other bulbs. LED lights actually have more in common with your TV than with the other light bulbs you have. That's because LEDs are tiny semiconductor devices that can produce directed light in an extremely efficient manner. (Another fun fact is that there’s no such thing as a white LED light—white is created through combining red, green and blue LEDs.)
Photo from Shutterstock
As you can see in the above photo, you can get LEDs in a bulb shape that mimics incandescent bulbs and fits in the same sockets. You can also get LEDs in embedded or integrated forms, like in under-cabinet lights, tape lights or fixtures that have really out-of-the-box designs. These cool, inventive looks are made possible by LEDs being super tiny!
You can find LED light sources in a wide variety of color temperatures. If you like the warm white glow you'd get from incandescent bulbs, you can certainly find that in LED. But if you prefer something in a cool white, there are LEDs to fit that bill too.
LED lights also last much longer than their fluorescent, halogen or incandescent counterparts—sometimes as long as 20 years! (Yes, years.)
Common Sizes of Bulbs
This is not a totally exhaustive list, but just includes some bulbs you’ll most likely encounter on our site.
Standard or E26: This is the screw-in bottom type bulb you probably imagined when you thought of a light bulb earlier. It is also called medium base sometimes. E26 stands for “Edison” and the 26 is the base’s width in millimeters. Its bulbous shape is officially called A19 (“A” stands for “arbitrary” and the 19 means how wide the bulbs is at its widest point: 19/8”, or 2 3/8” if you don’t like improper fractions).
Most often seen in: pretty much every type of fixture. Chandeliers, pendants, outdoor lights, bath bars, ceiling fans, you name it.
Candelabra or E12: This is a smaller screw-in bottom bulb. E12 means Edison base with a 12-millimeter base width. There are lots of different shapes and sizes of candelabra bulb available depending on the effect you want to create.
Photo from Shutterstock
For example, there’s the C bulb, which you might recognize from Christmas lights. There’s also the B bulb, which has a longer and more torpedo shaped look. The G bulb is globe-shaped. The T bulb is tubular with a blunted end. The CA bulb is designed to mimic the look of a lit candle, sometimes even with “flicker” effects!
You might also find candelabra bulbs that have an even smaller screw-in base, such as E11 or E10. But E12 is the most common size for candelabra bases.
Most often seen in: chandeliers, pendants, some ceiling fans.
PAR: PAR is a screw-in base bulb shape that has a spotlight-shaped look.
Photo from Shutterstock
PAR can stand for two different but similar things: parabolic aluminized reflector or pressed-glass aluminized reflector. This means there’s a reflector inside the bulb that gathers up and concentrates the light. The most common size is PAR38, though others are available.
Most often seen in: track lights, recessed cans, certain outdoor fixtures like flood or spot lights.
GU10: This bulb is unusual in that it doesn’t have a screw-in base at all.
Photo from Shutterstock
Instead, it has two pins that insert or twist and lock into the base of the fixture. Its shape is called MR, which means “multifaceted reflector.” That’s because there’s a pressed glass reflector inside the bulb, like with PAR. MR16 is the most common size, though other sizes are also available.
You may also find GU bulbs in smaller sizes, like GU5.3, though 10 is the most common.
Most often seen in: recessed cans, track lights, certain outdoor fixtures like flood or spot lights.
G9: This is a very small bulb with a bi-pin base that features two looped prongs.
Photo from Shutterstock
(It looks almost like the handle on a pair of scissors, but if both parts of the handle were the same size.) It is most often seen in a tubular shape with a little nub at the top. While halogen G9 bulbs are common, LED options are readily available as well. In fact, the photo above shows an LED version!
Most often seen in: under-cabinet lights, certain bath bars, certain landscape lights.
Color Temperatures of Bulbs
Color temperature, also known as light appearance, tells you what kind of glow you can expect from a bulb. (Like the yellowy-white and the bluish-white discussed earlier, for example.)
It is measured in degrees Kelvin, or K. A yellow-white light, or warm white light, is usually about 2700K. A blue-white light, or cool white light, is usually about 3500K. As the color temperature grows higher, the glow of the light grows cooler, meaning it goes from yellow to white to blue.
If you're looking to buy a light fixture with integrated LED lights, that fixture's specifications will make note of the color temperature in those lights.
Light bulb boxes also give you this information on the Lighting Facts label.
If you're ready to shop, check out our selection of bulbs here.
Still got questions about light bulbs? We’re here to help illuminate you. Call us at 1-866-688-3562 or email us.
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Emma Harger-Young - LightsOnline.com