Compact fluorescent lights for cannabis plants Compact fluorescent lights are also known as CFL lights and they are commonly used for indoor purposes. They are energy sufficient and produce very little heat so you can place them as close to your plants or a few inches away. The efficiency of these lights ranges from 75 to 98 lumens per Watt consumed Bulbs in the 2700k to 3000k range provide higher yellow or red spectrum which promotes flowering. CFL grow lights in the 5,000k to 6500k range ...