How to Read an LED Bulb Package: Lumens, Color, and Fixture Fit

The FTC's consumer page is blunt: people used to shop by watts, but wattage only tells you how much energy a bulb uses. Lumens measure brightness. A traditional 60-watt incandescent made about 800 lumens. An LED can make those same 800 lumens on about 9 watts. Once you know the lumen number you want, the Lighting Facts label on the package is the comparison sheet: brightness in lumens, estimated yearly energy cost, expected life in years, light appearance (warm to cool), wattage, and whether the bulb contains mercury. LEDs do not contain mercury. Compact fluorescents do, which is why that line still exists on the label template.

ENERGY STAR's Light Bulb Purchasing Checklist is the decoder ring for people who still think in incandescent watts. To replace a 40-watt incandescent, look for at least 450 lumens. For 60 watts, 800 lumens. For 75 watts, 1,100 lumens. For 100 watts, 1,600 lumens. For 150 watts, 2,600 lumens. Those are minimum light-output targets on the checklist, not a promise that every 800-lumen LED will look identical in your shade. A dark, narrow shade eats lumens. A clear globe in a hallway does not. The lumen number is still the only brightness figure the federal label requires you to be shown.

Read the Lighting Facts panel as a comparison sheet, not as the whole story. Brightness in lumens is the number to match. Estimated yearly energy cost is a modeled figure at a stated electricity price and hours of use, meant for comparing packages, not for predicting your bill. Life in years is a converted rated-life claim, usually assuming about three hours a day. Light appearance is Kelvin, warm to cool. Watts are input power. Mercury should read none on an LED. CRI, enclosed-fixture rating, and dimmer compatibility are not on that panel. They live in the rest of the fine print.

Color appearance and color accuracy are different quantities, and the aisle conflates them. Correlated color temperature (CCT), in kelvin, is what the Lighting Facts 'light appearance' bar shows. ENERGY STAR's checklist maps the common residential points: 2700K as warm white, the old incandescent color; 3000K as soft white; 3500K as a cooler white often used in kitchens and work spaces; then 4100K, 5000K, and 6500K toward daylight. Lower kelvin looks yellower. Higher kelvin looks whiter or bluer. That is appearance, the color of the light itself.

Color rendering index (CRI, reported as Ra) is how accurately that light reveals the colors of objects compared with a reference source. The Lighting Facts label does not have to print it. ENERGY STAR's lamps specification does: a solid-state lamp must have Ra of at least 80, with limits on how many sample units can fall below 77, and none below 75. The Department of Energy's purchasing page repeats the same floor: ENERGY STAR-qualified bulbs must have a CRI of 80 or greater. If you are matching paint, food, or skin in a bathroom, look for CRI 90 on the fine print or the manufacturer's spec sheet. If the package is silent, assume you are getting the ENERGY STAR minimum or less, not a studio lamp.

Heat is why enclosed-fixture rating is not fine print. An LED's driver and diodes live in the same small envelope that used to be an empty glass bulb. A fully enclosed globe, a recessed can with a sealed trim, or an outdoor wall lantern with a glass door traps that heat. ENERGY STAR's specification treats 'not for use in totally enclosed luminaires' and 'not for use in recessed luminaires' as labeling that changes which tests apply. If the package does not say the bulb is rated for enclosed fixtures, do not put it in one and then blame the 15,000-hour claim when it dies in two years. The Department of Energy's purchasing guidance says the same thing in plainer language: when buying for fully enclosed fixtures, check the packaging or technical specifications.

Dimmers are a second compatibility problem, not a brightness problem. Incandescent dimmers chopped a resistive load. Many LED bulbs are a switching power supply. ENERGY STAR's checklist tells you to look for a bulb marked Dimmable, and the specification's definition of dimmable is operational: the lamp must be able to go down to 20% output or lower with a suitable control. 'Works with most dimmers' is advertising. A compatibility list on the manufacturer's site, naming the dimmer models they tested, is a specification. If your dimmer is a 1990s rotary designed for a 150-watt incandescent, even a marked-dimmable LED may flicker, drop out at the bottom of the travel, or buzz. The fix is sometimes a dimmer listed for LEDs, not a brighter bulb.

Rated life is the number people treat as a guarantee. ENERGY STAR's lamps specification sets floors: omnidirectional and decorative LED lamps must have a rated life of at least 15,000 hours; directional lamps at least 25,000 hours. Those hours are lumen-maintenance claims, commonly to L70, meaning the point at which the lamp is estimated to have fallen to 70% of initial output, based on standardized tests (including 6,000-hour lumen-maintenance data and, for longer claims, projections). The Lighting Facts 'life in years' line usually assumes about three hours of use per day. A 15,000-hour claim at three hours a day is about 13 years on paper. It is not a promise that a bulb in a sealed porch fixture, on a dimmer, in a 90-degree attic, will still be at 70% in 2039. ENERGY STAR also ties warranty length to the life rating (a 3-year minimum warranty for lamps rated 15,000 hours or more, based on three hours a day). Read the warranty. It is the only part of the life claim that is a commercial obligation.