LED 101: Your cheat sheet for the light bulb aisle

Rising efficiency standards have transformed your local store's lighting aisle into LED central, and that means that there are some new things to understand if you want to be sure to buy the right light bulb for your needs. We've got your back, though -- just click through for quick primer on what you'll want to know and look for.

Light bulbs are just devices that convert electricity into light. Old-school incandescent bulbs like this one do it by using electricity to heat up a wire-like tungsten filament to the point where it glows. It works like a charm, but it isn't efficient, because the majority of that electricity is getting converted into heat, not light.

That's where these new LED bulbs come in. They put out the same amount of light as incandescent bulbs, but they use much less electricity to get the job done. For instance, this 100-watt replacement LED puts out the same amount of light as a 100-watt incandescent, but it only uses about 15 watts to do it. Use each for an average of 3 hours per day for a year, and the incandescent will add about $12 to your energy bill. The LED will add just $2 to it. Even if the LED costs more upfront, it's still the cheaper option in the long run -- and these days, most LEDs will pay for themselves in energy savings within a single year.

LED stands for "light-emitting diode." Each of those diodes is just a little electrical component that emits light when electricity passes through it.

The biggest thing most shoppers look for are light bulbs that are bright enough for their needs. The term to know here is "lumens," a unit of measure for brightness. The more lumens a light bulb has, the brighter it is.

The confusing thing about that is that most of us are accustomed to talking about brightness in terms of wattages, as in "60-watt bulbs." That's why most LED manufacturers list their bulbs using terms like "60-watt replacement." They're saying, "This LED is bright enough to replace an old 60-watt bulb."

That's all well and good, but it's the lumens that actually matter as far as brightness is concerned. Stick to these figures as you shop, and you'll avoid buying a bulb that's disappointingly dim:

40-watt replacement: Look for at least 450 lumens
60-watt replacement: Look for at least 800 lumens
75-watt replacement: Look for at least 1,100 lumens
100-watt replacement: Look for at least 1,600 lumens

The key here is to look for the "Lighting Facts" label that manufacturers are required to print on their packaging. Just like the Nutrition Facts labels on your food, it's filled with useful info about the bulb you're buying -- things like lumens, wattage, yearly energy cost, expected lifespan and color temperature.

You'll also want to think about directionality before you make a purchase. Some bulbs are designed to put light out evenly in all directions, while others, like that bulb on the left, aren't as good at it. It's especially important if you need a bulb that puts out a lot of downward light, for a reading lamp for example.

If that's the case, look for bulbs that claim to put out "omnidirectional" light. That means that they promise to shine evenly in all directions.

Color temperature is another light bulb basic worth familiarizing yourself with. It isn't a measure of heat, but rather, a measure of a bulb's specific white-light color tone. The scale typically ranges from 2,700 K up as high as 6,000 K or above, with warm, orange-like tones at the bottom and hot, bluish-white daylight tones at the top.

2,700 K bulbs like that one on the left are the ones you're probably used to, and they're typically better for subdued, relaxing lighting. Daylight bulbs like that one on the right can help trick your brain into thinking it's daytime, keeping you more alert.

The easy way to remember color temperature is to think of a flame. It starts out orange, but when it gets really hot, it turns blue.

You can see the subtle impact of different color temperatures in this comparison shot. I tend to like bulbs in that middle ground -- a little yellowy, but not too yellowy. To each their own, though!

Another metric worth thinking about is color rendering, or how accurate and vivid a given bulb will make whites and colors look. For reasons that are pretty wonky, most LEDs struggle with reds, and a lot of those yellowy 2,700 K bulbs will cast a yellowy tinge on things. Bulbs that are good at color rendering, like that GE Reveal bulb on the right, can help fix that.

We're seeing a growing number of bulbs that claim to offer improved color quality, but they've been largely inconsistent in our tests. If color quality is important to you, my advice is just to stick with GE Reveal bulbs, which are all designed specifically with color quality in mind. I've tested about a dozen of them by this point, and they always do a great job in my color tests.

Like other kinds of light bulbs, LEDs come in all shapes and sizes, and you'll want to know which one you need before you start shopping. BR30 floodlights like that LED on the left put out all of their light in a single direction, making them a good pick for overhead fixtures that shine straight down. That PAR38 floodlight on the right is weather-rated, making it a good pick for outdoor use.

If you don't want to get confused at the store, you can always take the bulb you're replacing with you. Most lights print specs like lumen output, power draw and color temperature directly on the bulb itself, making it easy to compare as you shop.

Just like your phone or laptop, LED bulb performance is affected by heat. As you leave the bulbs on and they heat up, the brightness will dip slightly. After 45 minutes or so, the light output will stabilize as the bulb's heat sinks kick in. Brightness and efficiency is measured after the bulbs hit this "steady state," so you aren't getting shortchanged, but it's worth knowing.  

We measure this loss of lumens with every bulb we review. Bulbs that finish higher in this test typically have better heat sinks, making them easier to recommend.

We also test the dimmability of every LED bulb we review. There are still some sticking points here, with bulbs that flicker or buzz due to electromagnetic interference when you dim them up and down, and your mileage may vary depending on the specific hardware in your home. For that reason, I recommend hanging onto your receipt and the bulb's packaging if you're buying an LED with the intention of dimming it. Most big-name hardware stores have helpful return policies if you run into any trouble.

One of the biggest trends in the lighting aisle these days is vintage-style LED bulbs that are designed to mimic old-school incandescents in artful ways. Some, like this Feit bulb, are pretty striking to look at, and can make a good pick for exposed bulb lighting setups where you want to strike a classic ambiance. (Trendy restaurants have been using this trick for years to set mood lighting.)

The "filaments" inside these vintage-style bulbs are actually just thin strips of LEDs. I really like this double helix design because the diodes all face outwards and don't cast any shadows.

Other vintage-style bulbs use different layouts, and some, like this Philips Warm Glow LED, will cast undesirable shadows if the fake filaments get in the way of each other.

Another caveat: Look out for misleading claims about brightness from vintage-style LED bulbs, because they tend to futz around with the terminology more so than other, non-decorative categories. 

In this case, a "60-watt replacement" should put out at least 800 lumens of brightness. 300 lumens isn't even close.

One last thing: Now is the perfect time to think about upgrading to smart lighting. With most smart bulbs, you can program your lights to turn on automatically at sunset or when motion is detected, or you can program scenes for things like dinner and movie night that give you the exact brightness settings you want whenever you want them.

For me, the biggest selling point is that smart bulbs are great at dimming. You don't need any dimmer switches to use them, because the dimming mechanisms are located in the bulbs themselves. In almost all cases, they'll dim without flickering or buzzing.

Prices have fallen considerably, too. For instance, this Eufy Lumos LED costs less than $20, and it doesn't need a hub. Just screw it in, sync it with your phone and start automating.

Along with falling prices, you've got a growing diversity of options. These Sylvania smart bulbs come in a variety of shapes and sizes, and the regular A-shaped one in the middle costs just $12.

Some smart bulbs will even change colors on demand. They tend to cost a bit more, though, typically at least $30.

One of the big drivers of the current smart lighting boom: Alexa, and other voice assistants like her. If you want bulbs that she can turn on and off, you're in luck -- and we've got some suggestions.