I'm running a compact flourescent spot light from home depot. (I think its day light 5100K--said so on the back of the package). Its like a 16W or something.. WORKS EXCELLENT. I just started and threw 2 balls in there an in 1 week it has doubled in size.. Another week or so and I will have to start harvesting. Came in a 2 pack for like 20 bucks or less.