The EnergyLight yields between 2,500 and 10,000 lux, depending on how far you sit from it. Lux (abbreviated as lx) is the unit of illumination. People need a certain intensity of light each day to feel fit and healthy. In winter, the amount of light outside on a cloudy day may be as low as 1,000 lx, whereas on a sunny summer day it sometimes exceeds 100,000 lx. Even in a well-lit room, the amount of light usually does not exceed 500 lx.