Well, that question is rather debatable. Many use HID, HPS lighting, however these lighting systems can be quite expensive as well as very costly on your electric bill. I've been using CFL (Compact Flourescent Lighting). They give out very low heat, while still emitting the spectrum your plants require. However I wouldn't recommend these for a large grow, of let's say 5 or more plants. A 23 watt cfl is approximately equivelant to a 100 watt incandescent, thus saving you much money. I use 3 for one plant. One on top and two on the sides to reach the lower buds. Happy Smoking.
