Lumens per Watt
The efficacy of a light source is a ratio of the amount of light produced (in lumens, lm) to the electrical power consumed (in watts, W). This is the lm/W figure and it is useful for comparing efficacies of different light sources. For example your staple MR16 tungsten halogen from a few years back would have been around 15-20lm/W, a typical Xicato LED module we now use in the TTX2.70 can achieve up to 136lm/W. What this figure does not take into account is the effect of the power supply or driver on the efficacy of the light fitting as a whole, for that you need to consider the lumens per circuit watt.

Lumens per circuit watt
Drivers and power supplies have some electrical losses, we try to use the most efficient drivers and power supplies to minimise losses but nevertheless the light source efficacy is reduced a little. Lumens per circuit watt figures provide a useful means of comparing different light fittings to one another.

We will happily provide information on the efficacy of our light sources and our light fittings should you require it.