LED bulbs explained: lumens, kelvin, E27 and E14

For years, we bought light bulbs by watts: 40 for a bedside lamp, 60 for a table lamp, 100 for the ceiling. LED bulbs use so little power that watts no longer tell you much. Here is what to look at instead.

Lumens: how bright

Lumens measure the amount of light a bulb gives. More lumens means more light. As a rough guide:

• about 250 lumens is like an old 25 watt bulb, for a night light or a decorative lamp,
• about 470 lumens is like 40 watt, for a bedside lamp or a chandelier,
• about 806 lumens is like 60 watt, for most table and floor lamps,
• 1500 lumens or more is like 100 watt, for a ceiling light in a large room.

Our LED bulb E27, warm white, 3 pieces, gives 806 lumens for only 7 watt. The LED candle bulb E14, 3 pieces, gives 470 lumens for 4 watt.

Kelvin: the color of the light

White light comes in many colors. Kelvin, written as K, measures it. A low number is warm and yellow; a high number is cool and blue.

• 2700 K is warm white, like an old bulb. Cozy for a living room and a bedroom.
• 4000 K is neutral white. Good for a kitchen, a bathroom and a desk.
• 5000 K and more is cool daylight. Good for a workshop or detailed work.

Can’t decide? The LED desk lamp with dimmer has all three, and the Zonnewende smart LED bulb E27, color, changes from warm to cool from your phone.

E27 and E14: the fitting

The fitting is the screw thread at the bottom. The number is its width in millimeters. E27 is the large, common fitting in table lamps, floor lamps and pendant lamps. E14 is the narrow fitting in chandeliers, wall lamps and small lamps. Check the old bulb or the label inside the lamp before you buy. The two don’t fit each other.

Dimmable or not

Not every LED bulb can be dimmed. A bulb that isn’t dimmable flickers or hums on a dimmer switch. Check the pack. Our basic E27 and E14 bulbs are not dimmable; the smart bulb dims from the app.

Why it is worth switching

An LED bulb uses about a tenth of the power of an old bulb and lasts about fifteen years at a few hours a day. That saves money every month and saves you climbing on the household step ladder, 3 steps, to change bulbs.