LED bulb: cap, lumens and light color

1. Identify what the luminaire accepts

Turn off the power supply before handling according to the luminaire's instructions. Note the existing bulb cap, its shape and dimensions available under the shade or in the spot. Read the limits and conditions indicated by the luminaire and the new bulb. A screwing bulb is not automatically suitable for all environments or control devices. In case of doubt about the installation, have the relevant point checked before purchasing rather than multiplying the tests.

• Cap and dimensions raised.
• luminaire instructions consulted.
• Dubious installation checked before purchase.

2. Separate amount of light and color

The ADEME recommends comparing the lumens for the light emitted and explains that the color temperature, in kelvins, describes the atmosphere. Choose according to the use: reading, circulation or lighting of a specific area. Do not replace this information by the number of watts or a photograph of the room. For several bulbs visible together, also bring their characteristics together in order to avoid a mixture of unwanted atmospheres. No single level of lumens is prescribed here for all rooms.

• Lumens up.
• Colour temperature selected.
• Use and combination of specified bulbs.

3. Checking Dimmer and Added Functions

If your lighting uses a dimming device, look for an explicitly announced compatibility between the lamp and the device. For a connected bulb, raise the necessary elements: application, protocol, possible additional equipment and control mode when the network is unavailable. The price of a single bulb does not describe the cost of a complete system. Make a distinction between simple replacement and change of functions, then compare only configurations capable of rendering the service expected.

• Variant and compatibility identified.
• Decounted network accessories or equipment.
• Order without service included annex.

4Convert power to an explicit cost

Ficile example: a light bulb of 8 W used 1 000 hours consumed 8 × 1 000 Φ 1 000 = 8 kWh. At a fictitious rate of 0,25 €/kWh, it represents 2 Use the actual power, not a commercial equivalence with an old bulb. Compare the same hours and add the purchase price if you are close to budgets. Conditions of use and a breakdown can change the total expenditure: the indicated life is not a certain duration to be entered in the calculation.

• Real Watts distinguished from equivalence.
• Same number of hours for offers.
• Tariff and duration retained as assumptions.

Fictional example · No merchant prices

Compare equal lumens before calculating watts

Fictional example: two bulbs compatible with the same fitting each provide 800 lumens at the same colour temperature. A costs €6 and uses 8 W; B costs €4 and uses 12 W. Over 3,000 hours at a constant €0.25/kWh, electricity costs €6 and €9. Including purchase, totals are €12 and €13. A’s additional purchase cost is offset after 2,000 hours in this scenario, assuming both bulbs remain usable throughout.

• Check cap, dimensions, lumens, colour temperature and dimmer compatibility.
• Calculate kWh as watts × hours ÷ 1,000.
• Do not infer actual lifespan from rated power alone.

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