Reading the Lighting Facts label

Bulb packaging is mostly marketing, with one exception: a standardized panel, usually on the back or the side, that presents the same figures in the same order on every box. It exists precisely so you can compare two bulbs without decoding two different marketing vocabularies.

Learning to read it takes about a minute and it is the difference between buying on a photograph and buying on a specification.

Brightness is the number to read first. It is the only figure that tells you what the bulb does, and it is the one that makes the whole method in how many lumens does a room need possible, because lumens add up across fittings.

Light appearance is second, and it is a scale rather than a single point - most panels show a slider from warm to cool with the bulb's position marked. 2700K sits at the warm end and is this site's default for living spaces. What each step actually looks like is in the light bulb color temperature chart.

Estimated yearly energy cost is calculated on a fixed assumption - three hours of use per day at a standard electricity rate. Neither will match your house. A porch light running dusk to dawn runs far more than three hours; a closet light runs far less. Treat the figure as a way to rank two bulbs against each other, never as a prediction. The real arithmetic is in what does an LED bulb cost to run.

Life in years is the same rated-hours figure divided by that same three hours a day. A bulb showing "22.8 years" is a 25,000 hour bulb, and it will reach that only in the conditions the rating assumes: an open fixture at normal room temperature. Put the same bulb in a sealed porch lantern and the number means very little - which is the subject of best LED bulbs for enclosed fixtures.

The Cree A19 is a good example of a bulb that publishes both halves honestly: a 25,000 hour rated life and an explicit statement that it is good for enclosed fixtures. The second claim is what makes the first one credible in a real fitting.

The panel's real limitation is what it leaves out. Four specifications that change whether a bulb is right for your fitting are simply not on it.

• CRI. The biggest gap. Color rendering decides whether food, skin and fabric look right, and two bulbs with identical panels can differ enormously. Manufacturers who do well on it advertise it on the front - the Philips at CRI 95 and the Waveform at 95+ with R9 80+ both do. Silence on CRI usually means around 80. The case is in best high-CRI LED bulbs.
• Beam angle. Absent from the panel, and it decides where the light lands. The Yuji CRI-MAX BR30 publishes a 180-degree beam separately, which is why it can be specified rather than guessed - see beam angle and spread.
• Enclosed, damp and wet ratings. Printed elsewhere when stated at all. Absence is not permission.
• Dimmer compatibility. "Dimmable" appears on the front of the box; which dimmers it actually works with almost never does. That is the subject of LED dimmer compatibility.

So the practical routine is: read the panel for lumens and Kelvin, then look at the rest of the box for CRI and the ratings. If the second set is missing entirely, you are looking at a bulb sold on price.