The right LED light is picked by fixture fit first, then lumens, color temperature, dimmer compatibility, and an ENERGY STAR label.
Grab the wrong bulb and you find out at the register — or on a ladder with a base that won’t turn. The job comes down to five things: the fixture, brightness in lumens, color, dimmer compatibility, and lab testing.
Start With Lumens, Not Watts
Brightness is measured in lumens; watts only tell you energy burned — shopping by wattage is how you get a reading lamp that feels like a parking lot. ENERGY STAR’s purchasing guide makes the distinction plainly: lumens indicate light output, watts indicate energy consumed.
Use your old incandescent as the anchor. ENERGY STAR’s targets: a 40-watt incandescent is roughly 450 lumens, 75-watt about 1,100, 100-watt around 1,600, and 150-watt near 2,600. A modern LED hits those numbers while drawing a fraction of the power.
Match the job to the room: hallways and lamps run fine around 450 to 800 lumens, kitchens and workspaces want 1,100 to 1,600, and a bright utility area can go higher.
Match the Bulb to the Fixture Before Anything Else
Shape and base come first — a bulb that doesn’t fit the socket can’t light anything. Check packaging for proper use and match the base: standard screw-in E26, smaller E12 candelabra, pin-style GU24, and two-pin GU5.3 in some recessed fixtures.
One caveat: ENERGY STAR notes its labeling program for the most common light fixtures has ended, and only high-performing recessed downlights still earn the label. The label on the bulb is your most reliable signal now.
Two numbers set the mood. Color temperature in kelvins decides warm versus cool — around 2700K reads soft and yellow like an old incandescent, 3000K is clean warm white, and 4000K and up turns crisp and blue-white for garages and task areas. The second is CRI; stay in the mid-to-high 80s at least for home use, since low-CRI bulbs make wood, fabric, and paint look muddy.
If the fixture sits behind a dimmer, motion sensor, or photocell, compatibility is not optional. Buy bulbs marked Dimmable and confirm bulb and dimmer work together — a mismatched pair flickers, buzzes, or drops out at low levels.
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Replacing An Old Bulb: Lumens, Power, And Fit
The table maps the bulb you know to the LED you should buy, using ENERGY STAR’s targets. Match on lumens, not the wattage on the new box.
| Old Incandescent | LED Brightness (Lumens) | LED Power Draw |
|---|---|---|
| 40W | About 450 lumens | 9–13W |
| 60W | Roughly 800 lumens | 8–12W |
| 75W | About 1,100 lumens | 18–25W |
| 100W | Around 1,600 lumens | 23–30W |
| 150W | Near 2,600 lumens | 30–52W |
| Warm white (2700K) | Soft, yellow-white feel | Lamps and bedrooms |
| Cool white (4000K+) | Crisp, blue-white feel | Garages and task areas |
The Department of Energy’s consumer guidance boils fixes down to replacing bulbs you leave on three or more hours a day with ENERGY STAR-qualified LEDs. The ENERGY STAR light bulb purchasing guide carries current replacement numbers.
Four mistakes cause nearly every disappointing LED purchase: buying by watts instead of lumens, assuming any bulb dims cleanly, skipping the shape and base check, and ignoring color temperature and CRI.
FAQs
Are all LED bulbs dimmable?
No. Only bulbs labeled Dimmable are built for dimmer switches. A non-dimmable LED on a dimmer will flicker, buzz, or shut off at low settings. Even dimmable bulbs need a compatible dimmer — check for the NEMA LED Dimming Compatibility logo on both bulb and dimmer.
What color temperature should I pick for a living room?
Around 2700K to 3000K suits living rooms, bedrooms, and dining areas because it mimics the warm glow of an old incandescent. Save 4000K and higher for garages, basements, and task lighting. Aim for a CRI in the mid-to-high 80s.
How bright is a 100-watt replacement?
About 1,600 lumens, per ENERGY STAR’s targets, while drawing only 23 to 30 watts. Don’t shop by the wattage comparison on the box — match the lumen number to the brightness you want.
Do I still need to look for the ENERGY STAR label?
Yes, especially on the bulb itself. It means the bulb was independently certified and tested for performance and energy savings. The fixture program has largely ended, and only high-performing recessed downlights still earn the label.
References & Sources
- ENERGY STAR. “Light Bulb Purchasing Guide.” Supplies lumens-versus-watts guidance, the incandescent-to-LED replacement targets, dimming advice, and the fixture program notes.
- U.S. Department of Energy, FEMP. “Purchasing Energy-Efficient Light Bulbs.” Covers common ANSI base types and energy-efficient bulb purchasing.
- NEMA. “LED Dimming Compatibility Program.” Explains the compatibility logo and the 20 percent dimming floor.