LED lighting is lighting based on the light-emitting diode: a semiconductor that gives off light as soon as current passes through it. Unlike an incandescent lamp, the light is not produced by heating a filament but directly within the semiconductor material, so far less energy is lost as heat.
An LED lamp is more than just the diode: it always contains a driver that converts mains voltage to the right direct current, and a housing that carries the heat away. In practice those two parts usually determine the lifespan, not the LED itself.
What to look at when choosing
- Lumens rather than watts. The lumen figure says how much light the lamp gives; the wattage only says what it consumes. So compare lumens when replacing an old lamp.
- Colour temperature in kelvin. Roughly: 2700 K warm white (living room, bedroom), 3000 K warm neutral (bathroom, kitchen), 4000 K neutral white (workroom, garage), 6500 K daylight (workshop, plant room). For living spaces 2700–3000 K almost always feels better.
- Colour rendering (CRI or Ra). A value of 80 is standard; 90 and above is better in kitchens, bathrooms and anywhere colour matters. At low values skin and timber look dull.
- Beam angle. A narrow beam spot gives accent light, a wide beam gives general light. Two lamps with the same lumen output can look completely different.
- Dimmability. A lamp is only dimmable if it explicitly says so, and the dimmer must be suitable for LED. A mismatched dimmer is the most common cause of flicker and buzzing.
Energy label and consumption
Since September 2021 light sources in the EU carry an energy label on an A to G scale, using a stricter measurement method than the old label. The class follows from the efficacy in lumens per watt. Class A is very demanding and is reached by virtually no ordinary household lamp; good retrofit LED lamps generally sit in the lower half of the scale. That does not make them inefficient — compared with incandescent and halogen lamps the saving is large.
The packaging must also state power in watts, output in lumens, lifespan in operating hours, and the number of switching cycles.
Lifespan and heat
Manufacturers’ lifespan figures vary strongly by quality class: budget lamps around 10,000 operating hours, mainstream lamps in the order of 15,000 hours, and the most efficient versions considerably higher. The deciding factor is almost always heat dissipation:
- Do not build a downlight into an airtight enclosure unless it is expressly designed for it. Trapped heat shortens driver life dramatically.
- In an enclosed fitting or sealed shade, use a lamp released for that purpose (“suitable for enclosed luminaires”).
- Where there is insulation in the ceiling, only use downlights approved for insulation coverage; otherwise there is a fire risk. Check the marking on the fitting.
Points to watch during renovation
- Fix the lighting layout before plastering. Adding cabling and boxes afterwards is expensive and shows.
- Split your circuits sensibly. General light, accent light and task light on separate switches give far more usable rooms than one ceiling fitting.
- LED strip needs its driver in the right place. Provide an accessible, ventilated position — the driver will fail before the strip does.
- Use the same colour temperature within a room. Different whites side by side are noticed immediately.
Related terms
- Energy label
- Sustainable building
- Electrical installation
- Consumer unit
- Lighting design
- Dimmer
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.