My unit is in my basement. I have learned that it takes about 50 watts per square foot for an 8 hour period. My first setup attempt was severely inept. T8 light fixtures, not T5's like I had. I now have 6 light units instead of the 3 that I had. Lastly I am going to mount a spotlight on each side of the grow bed to use for spot lighting when needed. I will not be lacking for light now. I would definitely say overkill on lights is a good investment.