The lightstream, mesured in "Lumen" (abbreviated: lm), is the total light performance that is emitted by a light-source. For many consumers the wattage of a luminaire is the unit for performance. But it is just a unit to measure the power consumption of the lamp. In terms of energy-efficient alternatives, like LED lamps, the amount of Lumen is noted additionally. The more Lumen, the brighter the lamp.