LED Lamps - What You Need to Know

(14 Mar 2016)

In September, the manufacture of many halogen lamps will stop, thanks to the same legislation that saw the end of the trusty 100W incandescent lamp. This includes the most common type of lamp used in downlight fittings, the GU10. LED lamps are the obvious choice to replace these outmoded lamps but they are a little more complicated than their halogen counterparts. You may be thinking, 'Why can't I just pop to B&Q and get some new lamps?' Let our guide explain and help you avoid the potential pitfalls...

Colour Temperature

Colour temperature is measured in Kelvins (K). A traditional halogen lamp will have a colour temperature of around 3,000K. LED lamps are available in a range of colour temperatures, anything from 2,700K through to 5,000K or more. The smaller the number, the more yellow/orange ("warm") the light emitted appears and the higher the number, the more white/blue ("cold") the light becomes. So, if you replace one blown halogen downlight with an LED equivalent, the likelihood is the emitted light will look noticeably different to any halogen lights around it. A real shame if you've spent time creating a beautiful lighting scheme to illuminate your home!

So the best solution is to consider changing all the lamps in an area at the same time. If you're replacing halogen lamps, choosing an LED lamp with a colour temperature around 3,000K will provide the most comparable result.


The amount of light a lamp can emit is measured in lumens. With halogen lamps, the brightness of the lamp is proportional to its rated power consumption, so a 50W halogen lamp is brighter than a 20W halogen lamp and replacing a halogen lamp with another of the same rated power consumption will give you a very similar result. Unfortunately, this isn't the case for LED lamps; an 8W LED GU10 from one manufacturer may produce a different amount of light than an 8W lamp from another manufacturer. Again, the best course of action here is to use the same make and model of lamp throughout each area.

Heat Sinks and Fitting Depth

Unlike halogen lamps, LED lamps come fitted with heat sinks on the back to move the heat away from the internal chip and prevent overheating. Consequently, LED lamps typically require more depth in the ceiling than their halogen equivalents. Normally, this is easily accommodated in renovations and new builds, but in a retrofit scenario this could prove problematic. It's best to check the depth you have available before purchasing any LED lamps.

Dimming Systems

Many houses contain at least some dimmable lighting circuits, whether it's a simple rotary dimmer on the wall, or a whole home intelligent lighting system, like Lutron or Control4. If you plan to replace your halogen lamps for LED lamps on an existing dimmed circuit there are a few things to check:

Make sure the LED lamps you buy are 'dimmable' - many are not. If the lamp is dimmable, this should be displayed on the box. Trying to dim a non-dimmable LED will result in damage to the lamp and/or even the dimmer itself.

Most dimmers will have a minimum rated load expressed in Watts (W). Add up the rated power consumption of all the LED lamps on the circuit and, if the total is not above the minimum rated load of the dimmer, you will have problems, such as lamps that flicker erratically. If you have a Lutron or Control4 system, this requirement can be dealt with by choosing new dimmers from Lutron and Control4, which have minimum rated loads less than 1W, or by using Lutron synthetic loads which trick existing dimmers into thinking they're driving larger loads than they really are, without wasting lots of energy.

All dimmers also have a maximum rated load, but this specification is based on halogen lamps so, as a result, the maximum rated load will be much higher because the wattage is higher with halogen lamps, than with LED lamps. Unfortunately though, this maximum is not directly transferable to LED lamps because they behave very differently to halogen lamps. Instead, you should calculate 10% of the maximum rated load of your dimmer and use this as your maximum for LED lamps. For clarity, let's summarise: the total rated power consumption of all the LED lamps you are intending to put on a circuit should be between the advertised minimum rated load of your dimmer and 10% of the maximum rated load.

Even if you adhere to the three points above, some LED lamps simply aren't compatible with some makes and models of dimmers. They won't dim smoothly, and may flicker. One of the (many) reasons we love Lutron products so much is that they are as keen as we are on ensuring every installation of their equipment is successful. To help with this, they have set up the LED Centre of Excellence, who are responsible for testing as many LED products as possible on Lutron's range of dimmers. You can check if a lamp has been tested and if it's compatible here.

All in all, LED lamps can be very tricky to get right. The good news is, we're old hands. Why not give us a call on 0207 887 2424 for a chat about intelligent lighting and your home?

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