We only really think about light bulbs when it’s time to replace them. Then there’s a jumble of letters and numbers and bases to consider, and what the heck is a lumen anyway?
To answer all your most pressing questions about light bulbs, we’ve put together this handy guide. By the end, you’ll be able to tell the difference between BR and PAR, and why you should be more concerned with lumens than watts. Let’s start with bulb types.
There are four basic bulb types: LED, CFL, halogen, and incandescent.
LEDs (Light Emitting Diodes)
LEDs are essentially tiny semi-conductors that convert electricity into light. The chips are often housed in a protective dome that is sometimes coated to help produce a higher quality white light.
LEDs emit what’s known as cold light, which produces light without wasting energy on creating heat. They can be powered by batteries or even the sun, depending on the fixture.
They are resistant to vibration and shock and light up with no delays or flickers, regardless of how hot or cold the ambient temperature is.
As LED technology improves, each new generation of bulbs uses less and less energy to produce the same brightness. Plus, each bulb tends to last around 35,000-50,000 hours.
They come with a variety of bases and shapes, so they can be used in most common household fixtures.
You can even convert some fluorescent fixtures to LED with specially designed LED linear tubes. These “plug and play” tubes fit into existing fixtures without having to rewire or replace the ballast. Added bonus: they don’t contain mercury and won’t shatter since they’re not typically made of glass.
If you need a traditional A-shaped bulb, there are two models to be aware of: multi-directional and omni-directional bulbs.
Multi-directional models tend to have a large heat sink at the base of the bulb and emit directional light only. They’re great for pendants and sconces, but not so great for table or floor lamps.
Omni-directional bulbs emit light in all directions without casting unwanted shadows.
Since LEDs don’t have a filament, they don’t burn out like incandescent bulbs. Their lifespan is measured by lumen depreciation, or the decrease in brightness over time.
In fact, if you look on the packaging, you’ll often see a number called “L70” – that’s the point at which the LED produces 70% of its original brightness. When you see a lifespan of 50,000 hours, it really refers to the number of hours it takes for the LED to hit L70.
CFLs (Compact Fluorescent Lights)
CFL bulbs contain a ballast that drives an electric current through a tube. That tube contains the element argon and a special coating. As the argon is electrified, it generates invisible UV light that reacts with the coating to produce visible light.
If you’ve ever had a CFL in your home, you may have noticed that it can take a few minutes for them to reach full brightness.
They initially need more energy to light up, and that kickoff process can take up to 3 minutes. After the initial electrical push, the ballast regulates the electricity flow, making the CFL up to 70% more efficient than a traditional incandescent.
Some CFLs include decorative covers like a globe or reflector. Because of their unique shapes, these bulbs tend to start up a little more slowly than bare spiral CFLs.
CFL bulbs have an estimated lifespan of 7,500-20,000 hours. However, they can burn out earlier when used in short bursts. That’s why you’ll often see fluorescent tubes used in office buildings, where they’ll be on for extended stretches. Constantly turning them on and off can decrease lifespan significantly.
Keep in mind that most CFLs and fluorescent tubes aren’t made for outdoor use. They are prone to failure in colder temperatures.
CFL bulbs are available in all kinds of shapes and sizes, and can be used in nearly any fixture that uses an incandescent. Unfortunately, not all CFLs are dimmable. You’ll have to check the packaging to see which ones to use when you’re creating mood lighting.
Once upon a time, CFLs were only available in that bright bluish light you typically see in hospitals. These days they come in several color options, including ones that mimic the warm yellow tones of incandescent bulbs.
Remember that all fluorescents, including CFLs, contain small amounts of mercury. If one shatters, let the room air out for 10-20 minutes, and then carefully sweep up the debris into a sealed container. Avoid vacuuming, as that can kick chemicals up into the air.
Your best bet is to take tubes, CFLs, and broken fluorescent bulbs to a recycling center so they can be properly disposed of. Your neighborhood Orchard Supply Hardware store recycles these bulbs – simply take them to the customer service desk.
Halogen bulbs are really just incandescent bulbs that have a little halogen gas trapped inside with the filament. Like incandescents, halogens emit light because the electricity heats the tungsten filament until it is white hot, at which point it emits light.
The main difference is the halogen – it helps recycle burned-up tungsten gas, making the bulb use electricity in a slightly more efficient manner.
Halogen bulbs are not considered hazardous in the same way that CFLs are.
They use up to 25-30% less energy than incandescent bulbs, and have an estimated lifespan of 3,000-4,000 hours.
They are fully dimmable, just like incandescents. And unlike CFLs, they brighten instantly. Halogens are great for reading and task lighting, as the bright light can help reduce eye strain.
They’re also fantastic for display lighting – the white light, when focused on a point, makes colors appear more vibrant and helps highlight artwork, photos, and architectural details.
Halogen lights can also be used outdoors, and make great addition to floodlight and security light fixtures.
When you picture a light bulb, you’re most likely thinking of a traditional incandescent. A tungsten filament is enclosed in glass. Electricity heats the filament until it glows, and you have light.
Unfortunately, the bulb has to create a lot of heat in order to produce light, which is why it is a much less efficient energy user than halogens, CFLs, and LEDs.
Contrary to popular belief, incandescent bulbs are not illegal. The Energy Independence and Security Act (EISA, 2007) doesn’t directly ban incandescents – it simply sets guidelines for them to become more efficient. Only bulbs that do not meet current standards will ultimately go out of production.
In terms of up-front costs, these bulbs are generally the most cost effective. However, they use the most energy out of all 4 of the basic bulbs, which costs more in the long run.
If you’ve had incandescent bulbs for any period of time, you may be used to looking for bulbs based on watts. With more efficient options on the market, you should really be looking for lumens.
Watts are the measurement of power a light bulb uses. 40 watts means that bulb is drawing 40 watts of continuous power to stay on.
Lumens are the measurement of a light bulb’s brightness. The higher the number of lumens, the brighter the light.
Because many new bulbs are designed to save energy, the result is reduced wattage with higher lumens. That means if you’re relying on these wattage (rather than lumens), you could end up buying a bulb that is too dim or too bright for your home.
Most CFL and LED bulbs are marketed as replacements for incandescent bulbs of specific wattages, i.e. a 40-watt replacement LED bulb that really uses about 8 watts. Just remember – lumens are a much more accurate predictor of brightness.
If you’re switching from incandescent to CFL or LED, here’s what to look for in lumens:
How much light do you really need? Different rooms require different amounts, depending on what you typically do in that room.
Most rooms use a combination of ambient (overhead/wall-mounted) and task (spotlight/desk and table lamps) lighting. Here are our recommendations:
Ever notice how some spaces feel warm and others feel cold, regardless of the thermostat settings?
You’re probably experiencing the effect of color temperature, which can subtly influence your body and brain.
Color temperature has nothing to do with the actual warmth or coolness of the air, however. It’s a measure of the color that a light bulb produces, ranging from yellow to bluish.
Studies have shown that late night exposure to blue light can increase your body temperature and spur sleeplessness, while reddish hues have less effect on your natural circadian rhythm.
Yellow light (also known as warm light) is on the lower end of the scale, white light is in the middle, and bluish light (also referred to as cool light) is at the high end.
Light color temperature can be strategically used to your advantage in different rooms.
For a warm, cozy feel in your bedroom or living room, choose soft white or warm white.
For high-energy rooms like kitchens and garage workshops, go for bright white or cool white.
To really see a difference in color tones or take on detailed projects in bathrooms, kitchens, or basements, use a daylight bulb.
That leads us to Color Rendering Index (CRI), which measures how accurately a bulb shows colors on a scale from 1 to 100.
Think of it this way: if you’re in a dimly lit room, it’s really hard to tell which color is which because there is a lot of shadow. It’s the same with a room lit in a particular color – under reddish light, a green object may appear to be brownish or even black.
CRI scores are really only helpful for daylight, white, or natural lights. Anything rated over 80 will work well enough for your home. Generally speaking though, the higher the CRI, the more clearly a bulb will show different hues, from your accent wall to your favorite piece of wall art.
Bulbs come in a large variety of shapes, and those shapes are responsible for the letters and numbers you see on the bulb and its packaging. The letter abbreviations tell you what shape the bulb is classified as, while the number typically refers to the size.
Below is a chart containing abbreviations for different bulb shapes:
||WHAT IT STANDS FOR
||WHERE IT IS USED
||Lamps, hallway lights, and sconce fixtures
||Chandeliers and fixtures where the bulb is visible
||Flood lights or recessed cans
||Small appliances and indicator lamps
||Chandeliers and fixtures where the bulb is visible
||Bare light vanity bar
||Track and display
||Streetcar and locomotive headlights
||Outdoor lighting. Comes in short (S) or long (L) neck.
||Gimbal track rings, recessed cans, and weatherproof ourdoor spot or flood fixtures
||Signs and decorative
||Bankers’ lamps, podium lights, and fluorescent tube replacements
Once you know what kind of shape of bulb you need, the final piece of the puzzle is finding the right base. There are two main types: screw bases and pin bases.
Screw bases are the most common. Because the original incandescent is credited as Edison’s invention, bulbs with this kind of base are often referred to as Edison bulbs.
In halogens and incandescents, the screw base contains two contact wires joining the filament to the base, which connects electrical voltage to the light bulb.
The contact wires are soldered to the base metal at two different points so that electrical current can continuously flow through the wires to produce light.
More often than not, you’ll be looking for a medium base (standard bulb) or a candelabra base (smaller, typically found in chandeliers and night lights).
Pin bases are commonly found on MR16s, fluorescent tubes, and plug-in CFLs. They feature two or four pins that connect the light bulb to the electricity source. Some plug in, and some twist to lock into place. Electrical current then flows into the light bulb to energize the filament or ballast and generate light.