For a replacement bulb, start with the fitting: socket, supply voltage, available space, enclosure, and control. Then compare the lumens and appearance needed from the new lamp.
Compare costs at similar light output
Use actual input watts, annual operating hours, electricity price, lamp cost, and expected replacement labour. A “60W equivalent” label is not the lamp’s power draw. Check whether the compared lamps provide similar useful light.
Match the base and electrical rating
E26 and E27 describe nominal screw-base sizes; E12, GU10, and other bases describe different mechanical arrangements. A bulb that appears to fit is not automatically suitable for the supply or fixture. Check both ratings.
| Base | Identification check |
|---|---|
| E26 / E27 | Screw base; verify nominal size and the lamp and fixture voltage |
| E12 / E14 | Smaller screw bases; measure and confirm the specified type |
| GU10 | Twist-lock two-pin base; confirm voltage and lamp dimensions |
| GU5.3 | Two-pin base; confirm supply type and voltage rather than assuming compatibility |
Choose brightness and appearance separately
Lumens describe output, while CCT describes the appearance of white light. Check color rendering where objects or skin tones matter. View samples when replacing several lamps in a room.
Check the installation conditions
Recessed enclosures, ceiling fans, outdoor fittings, and emergency systems may need specific lamp ratings. Confirm dimmer compatibility, operating temperature, and whether a lamp is approved for the fixture.
Record the replacement specification
List base, voltage, dimensions, lumens, watts, CCT, Ra/R9 where relevant, beam angle, dimming, enclosure suitability, rated life, and warranty. Test a small representative group before replacing a whole building.
Frequently Asked Questions
Can an LED replace every incandescent lamp?
Check base, voltage, dimensions, enclosure conditions, output, and dimmer compatibility first.
Why can two lamps of the same watts look different?
They may differ in efficacy, beam distribution, CCT, color rendering, and optical losses.
