How much light do I need?
This is a question you may have, and it is one that is generally answered by the wattage of an electrical light. To know how much light a light source emits or how ‘bright’ a light is, the right parameter to check is lumens. Lumens is the measure of total amount of visible light available from a light source.
How to find the lumens?
Lumens output is mentioned on every light bulb and tube. It is generally denoted by ‘lm’ where other specifications such as wattage and voltage are written. For instance, a 40W incandescent produces 450 lumens. The same amount of light is produced by a 9W CFL and a 5W LED.
Most efficient lights
The best way to determine the efficiency of a light is to calculate the lumens per watt. Divide the lumens (lm) with the watts consumed, denoted by ‘W’. The higher the number, the higher will be the efficiency, it means that you get more light with less power input. For the 9W LED bulb shown in the picture, the lumens output is 900 lm and wattage is 9 Watts. So the lumens per watt is 100 lm/watt.
Typically, LEDs and some efficient t5 tubes have 100 lumens/watt efficiency. CFLs range from 50-70 lumens per watt and incandescent bulbs range much lower. Hence it is wiser to buy LEDs or high efficient tubes to save energy and the environment.
Image source: Author’s own