Choosing your LED bulbs: lumens, color temperature and buying tips

Since the end of incandescent and then halogen bulbs in the European Union, LED has become the standard for home lighting. But choosing an LED bulb means changing your frame of reference: the wattage no longer says much, and you need to look at the luminous flux in lumens, the color temperature in kelvins and the color rendering quality. Choosing well means getting the right ambiance in each room while using up to 80% less electricity than an old bulb. Here are the essential reference points.

Lumens replace watts

The lumen (lm) measures luminous flux, that is, the amount of light actually emitted, while the watt measures the power consumed. An LED produces much more light for much less energy: that is why bulbs are now compared on their lumen count rather than their old wattage. Here are the usual equivalences to recover the brightness of a classic bulb:

• About 470 lumens equals an old 40 W bulb
• About 800 lumens equals an old 60 W bulb, the most common wattage for living room lamps
• About 1,100 lumens equals an old 75 W bulb
• About 1,600 lumens equals an old 100 W bulb
• In LED, these fluxes correspond respectively to about 5 to 6 W, 8 to 10 W, 11 to 13 W and 15 to 18 W depending on the model

Color temperature: warm white or cool white?

Color temperature, expressed in kelvins (K), describes the tint of the light, not its physical heat. It strongly influences the ambiance of a room. There are three main families, from the warmest to the brightest:

• 2,700 K: warm white, the tint of an old incandescent bulb, ideal for the living room and bedrooms
• 3,000 to 3,500 K: intermediate warm white, a pleasant compromise for most rooms
• 4,000 K: neutral white, bright and neutral, suited to kitchens, entryways and work areas
• 5,000 to 6,500 K: cool white, close to daylight, mostly reserved for garages, workshops or highly technical offices
• In the living room, prefer 2,700 K; for reading or cooking, a neutral white at 4,000 K will be more effective

The color rendering index (CRI)

The color rendering index (CRI), rated out of 100, indicates how faithfully a source reproduces colors compared to natural light. A value of about 80 is acceptable for everyday use, but for the bathroom, kitchen or reading, choose a CRI above 90: the shades of food, clothing and skin are then rendered naturally. This is particularly important if you combine lighting and decoration: an LED with a low CRI distorts the colors of walls and fabrics.

The other criteria: base, dimmable and lifespan

• The base: E27 (large base), E14 (small base), GU10 (spotlights), and identify the base of your fixture before buying
• Dimmable: check the "dimmable" mention or the dimmer symbol if you plan to use it with a dimmer
• Lifespan: LEDs generally claim 15,000 to 25,000 hours, i.e. 10 to 15 years of normal use
• The energy label: since 2021, an A to G scale replaced the old A++; LEDs are generally rated A or B
• The luminous flux of the exact model: two LEDs of the same wattage can emit different amounts of light

Why LED is the most economical

A 9 W LED bulb replacing a 60 W one consumes about 80% less for equivalent lighting and lasts dozens of times longer. On a lamp lit 3 hours a day, the annual gain remains modest on the scale of a single bulb, but it becomes significant when you replace all the home's lighting, especially the spotlights that run for a long time. LED contains no mercury, unlike old CFL bulbs, and heats up very little: it does not warm the room in summer and presents no burn risk when touched after a few minutes of use.

The mistakes to avoid

• Choosing a bulb only on its wattage
• Putting 6,500 K cool white in a bedroom or living room: a clinical, unrelaxing ambiance
• Ignoring the base: an E27 bulb does not fit in an E14 socket
• Installing a non-dimmable LED on a circuit with a dimmer
• Buying very low-end LEDs without a reliable label: disappointing lifespan and color rendering

Choosing your LED bulbs therefore comes down to reading the label correctly: lumens for the amount of light, kelvins for the ambiance, a color rendering index for fidelity, and a base suited to your fixture. With these four reference points, you create lighting that is both pleasant and economical in every room, at a low purchase cost and with a lifespan of several years. Old bulbs, even the mercury-containing CFLs, are dropped off at the recycling center or the collection point at your hardware store.