Unlike watts, which express the energy consumption of an electrical device, lumens correspond to the quantity of light actually emitted by the lamp.This measurement is carried out by placing the lamp in an enclosure fitted with sensors and measuring the light emitted in all directions around the lamp.PLEASE NOTE! At equal power, all the lamps will not have the same lighting range because it will depend on how concentrated the beam at the exit of the lamp is (with a lens or a diffuser).The narrower the beam, the farther the lamp will illuminate.The wider the beam, the better the lamp will illuminate the sides evenly, but to the detriment of the range.