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The different types of light bulbs, explained

When you start browsing to find the best smart bulbs for your house, you’ll see that most of them are LED bulbs. To a newcomer, terms like “LED” can get a little confusing. Sure, LED bulbs are efficient, but how do they work? How different are they from fluorescent or incandescent bulbs? Which type of bulb is the right choice for the specific area you had in mind?

We’re answering all these questions with a complete guide on every type of residential light bulb you can buy, including what you should know about energy requirements and if it’s a good idea to buy.


Incandescent bulbs are the traditional option, the first type of light bulb invented and famous for their warm color. These bulbs use a filament, through which an electrical current is run. The filament has the right kind of electrical resistance to impede that current, which means some of the energy releases and shows up as light. This is also where we get the idea that more wattage (the power of the current) equals a brighter light, although this is only technically true for incandescent bulbs.

However, this approach also has its downsides. A lot of the electrical current is also expelled as heat, which makes incandescent lights hot and inefficient, wasting a lot of power that other bulbs can use — which means they cause higher energy bills. It also means the bulbs don’t last very long, usually a year or two at most, before they need to be replaced. That’s why you won’t find any smart bulbs that offer incandescent options, and why homeowners are incentivized to move away from incandescents and toward other lighting options.

Fluorescent tubes

via: Martine Laine/Flickr

Fluorescent tubes have a somewhat infamous reputation for providing the cold, unflattering lighting in school hallways and warehouses. But those tubes are actually very good at what they do — offering low-cost lighting with bulbs you don’t have to think about for at least several years.

That fluorescent tube you see is actually filled with a low-pressure, inert gas, typically argon, and a small bit of vaporized mercury (that mercury is why people are warned against approaching shattered fluorescent tubes for a while). The combination is very sensitive to an electrical current.

At either end of the fluorescent bulb is an electrode. A device called a ballast allows an electrical current to flow through the bulb from electrode to electrode in very short, very fast cycles. This energizes the gas mixture inside and causes it to produce lots of excess electrons. These electrons are in the ultraviolet spectrum so humans can’t see them, but that’s why fluorescent bulbs are coated with phosphor on the inside. Phosphor emits visible light when energized, so when the electrons pass their energy into the phosphor coating, it glows, producing the cool white light we see.

This happens many times a second as the current of electricity is cycled on and off, so it looks like a permanent glow to our eyes (hey, that’s a lot like how video fps works!) until the bulb wears down or breaks, which causes that telltale “flicker” of fluorescent tubes.

Yes, that’s all a bit complicated, but the results are clear: A reliable source of light that excels at lighting large areas and is about five times more efficient than incandescent bulbs. It’s not the friendliest-looking light, which is why people were hesitant to start using fluorescents in their homes. But when that started to happen, a new version of the fluorescent bulb was needed.

CFL (Compact Fluorescent Lights)

via: PickPic

The tube design of older fluorescent bulbs doesn’t really have a place in residential buildings, which is why you typically only see them in garages, closets, and inconspicuous spaces. Instead, homes have a lot of sockets designed for screw-in incandescent bulbs, posing a problem to fluorescent conversion.

The lighting industry solved this problem by adopting CFLs, or fluorescent bulbs shaped like incandescent bulbs that could be screwed into incandescent sockets. As the design of CFLs hints, they simply made a more compact version of the fluorescent tube, and wrapped it around itself in a bulb-like shape so that the two electrodes now rest beside each other, but still create enough current to energize the gas.

This compact design is more durable than the tubes, can work in home lighting sockets, and continues to save a ton of energy while lasting even longer than tubes — up to nine years in many cases. However, they can still struggle to emit “warmer” light.

LED (Light-Emitting Diode)

A diode is just a simple semiconductor that electricity passes through, a basic gateway for electrical current in electronics. Semiconductors are usually made with silicon that is “doped” or infused with a very specific mix of other elements to give it certain properties, such as a very finely tuned electrical resistance.

Going back decades, scientists have known that specific silicon formulas create diodes that glow when electricity is passed through them, similar to how phosphor glows from encountering electrons in fluorescent lights. It’s just how certain combinations of elements react to electricity. However, it remained nothing more than a novelty for years, until people started thinking: What if we made diodes glow as brightly as possible, and what if we packed those diodes close together to simulate the way a bulb works?

This turned out to be a fantastic idea, first for basic indicator lights on electronics, and then as a replacement for traditional fluorescent and incandescent bulbs. Diodes can be clustered together in all kinds of ways, making LEDs an incredibly versatile lighting option available in nearly any shape. As time passed, researchers found that specific silicon formulas could produce different colors of lights as well (some colors trickier than others), which is why LEDs are available in many colors and popular options for color-changing bulbs.

But LEDs have other key advantages as well. Unlike incandescents, they waste barely any energy and are an excellent choice for saving on electricity. Unlike fluorescents, they can come in a variety of tones and color temperatures to avoid problems with “cold” white light. Since there are no filaments, electrodes, or gases to worry about, LEDs are also incredibly long-lived and can last more than 20 years when designed properly.

All these features make LEDs perfect for smart lights and smart bulbs. While such bulb designs are usually made to imitate incandescent bulbs, inside is a cluster of LEDs lighting up together to produce the light-bulb effect.

HID (high-intensity discharge)

via: Wikimedia

HID bulbs are more unique types of bulbs that work in similar ways to fluorescent bulbs. They contain specific gas mixtures that are activated by an electrical current that creates a visible arc – for HID bulbs, no phosphor coating is needed.

Most HIDs today use sodium vapor or metal halide, although the first versions did use a type of mercury vapor. They specialize in producing a very powerful, very pure type of white light that’s excellent for visibility. That’s why you will see these bulbs used in professional photography, or as car headlights or searchlights. Sometimes they take the place of fluorescent tubes in arenas and other large spaces.

However, outside these specific applications, you don’t usually see HID bulbs used frequently. They can be expensive, it’s harder to make small versions of them, and they tend to suffer performance issues as they age, losing a lot of their brightness over time. That’s why you don’t usually see them in homes.


At a glance, a halogen bulb looks like an incandescent bulb, but it’s a bit more complicated, and the technology inside has a couple of key differences.

Like an incandescent bulb, halogen bulbs use a filament — in this case, one made of tungsten — to produce light. However, this filament is trapped inside a smaller inner bulb filled with halogen gas, a combination of iodine and bromine. This gas doesn’t really react to the current itself, but it does have a role to play: It creates a cycle that allows the tungsten filament to restore itself as it works instead of burning away.

In practice, halogen bulbs tend to last about the same amount of time as incandescent bulbs, about a year or two. But they burn very hot and create a high-quality white light, which makes them popular for accent lighting, floodlights, and various types of professional lighting. You won’t see a lot of them in a lot of residential spaces, but they can serve as alternatives to incandescents in the right spots. They are also somewhat notorious for being fragile due to their high heat, and respond poorly to residues or oils (aka, they can sometimes explode). Handle with care!

Special retrofits

via: US Army

While not exactly a bulb type, we do want to underline that CFLs aren’t the only bulbs designed for retrofitting. In fact, there’s a whole class of bulbs made just for retrofitting projects around the home when you need a new bulb for an old socket. These are usually LED bulbs with the diodes arrange in different patterns, plus different base types for various sockets. This helps guarantee that no matter what kind of lighting you have in your home, there is probably an LED retrofit made for it — including LED tubes that can fit into fluorescent tube sockets.

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