Why change from watts to lumens?
Because it tells us what we actually want to know – how bright a light will be. Lumens give us an easy way to compare the actual amount of visible light produced by any given bulb. For example, you could buy a 10 watt LED light bulb which would look much brighter than a 10 watt tungsten light bulb. This difference in brightness can only be characterised by the bulbs’ lumen output, i.e. how much visible light they are actually producing. Recent years have seen leaps forward in energy efficient lighting technology. Lighting accounts for approximately 20 % of global electricity usage, so these advances mean a dramatic reduction in carbon emissions, and new innovations will only improve the efficiency and quality of lighting. However there has been confusion over how new products compare to old in terms of brightness, which could be impeding their uptake. This is partly due to brightness being based on the electrical power input, or wattage. When incandescent bulbs were all pervasive, 100
