They may have to do so by 2020, when all general-purpose bulbs sold in America will have to produce 45 lumens per watt.
美国人可能不得不在2020年开始全面使用CFLs灯和LEDs灯，到那时在美国出售的所有一般用途的灯泡都必须产生每瓦45流明的亮度。
If people want to replace their old power-hungry incandescent bulbs with CFLs or LEDs good for 45 lumens per watt, all the better.
如果人们想要把他们的高耗能白炽灯换成45每瓦流明的CFLs灯或者LEDs灯，那就再好不过了。
While the upper limit for incandescent lamps is 52 lumens per watt, that is the theoretical luminosity of tungsten at its melting point.
虽然白炽灯的发光效率极限是每瓦52流明，然而这钨丝在其熔点的理论亮度。
While the upper limit for incandescent lamps is 52 lumens per watt, that is the theoretical luminosity of tungsten at its melting point.
虽然白炽灯的发光效率极限是每瓦52流明，然而这钨丝在其熔点的理论亮度。
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