Blog Post


Leading and Trailing Edge Dimmers Explained

The dimming of lights has always been very popular, as it is a quick and easy way to alter the ambience of a room.

When it comes to updating your dimmable lights to the more energy-efficient LEDs, what are the things we need to be aware of? How do we know what dimmers and lights bulbs we need?

Hopefully, this quick guide will give you a good basis of understanding of the different products on the market and which ones you will need.


When it comes to lighting, there are different dimming options to consider, each with different benefits and different functions. There are two types of dimming modules, leading and trailing edge, which we will look at below.


These dimmers were originally used for dimming incandescent and halogen lamps. Due to their original use, these dimmers have a high minimum load, making them less useful for low energy lighting such as LEDs.

The high minimum load requirements of leading edge dimmers mean you can struggle to meet this minimum with LED lamps and their low power consumption. Because of this you would have to use several LED lamps on one dimmer in order to meet the minimum load requirements of a leading edge dimmer.

Due to LEDs being more energy efficient, thereby producing more light with far less electricity, you could end up with more lighting than you need by using a leading edge dimmer set up. It is best to upgrade your dimmer switch to a newer trailing edge dimmer, which allows you to control lower wattage loads such as LEDs.


These more modern dimmers have many benefits over the leading edge type. These improvements include smoother dimming with less buzzing and interference. Trailing edge dimmers have a much lower minimum load than the leading edge, making them far more suitable for powering LEDs.

The 10% rule is very important when using trailing edge dimmers with LEDs. Although a 400W trailing edge dimmer may be able to power 400W of incandescent lamps with ease when it comes to LEDs the maximum load is only 10% of this. This means, with our 400W dimmer example, the maximum load would only be 40W worth of LEDs.

The main benefit of trailing edge dimmers is that they are able to control lower wattage loads. This means you do not have to worry about meeting the high minimum load of leading edge dimmers and can instead just use the amount of LEDs required for your lighting needs.


When dimming LED lamps, there are many things to consider:

  • Check the new LED lamps are dimmable before purchasing
  • Ensure your current dimmers are compatible with your new LED lamps. Well-known brands, such as Crompton, tend to have been tested with a wider range of dimmers, you can find a great range of LED lamps on our sister site, Green Lighting
  • Establish the minimum and maximum loads of the dimmer. This will allow you to know how many lights are needed on the circuit
  • It is recommended, to ensure the best quality dimming, that old leading-edge dimmers are replaced with the trailing edge
  • Ensure the maximum load of the dimmer (remembering the 10% rule for trail edge dimmers) is not exceeded by the total wattage of the LED lamps
  • Make sure you have a combination of dimmable lamps and dimmer modules that work together, before purchasing
  • You can guarantee compatibility by using Chip-On-Board fittings, such as the D-Lux LED Downlights with their electronically matched dimmer modules