sorry it is a 600w. I put my hand just above the seedlings and its not too hot...I think. they have their first set of true leaves already and they dont seem to be suffering (to my untrained eye). The temp in the room ranges from 65-75F. Night temps at the moment are pretty mild but as the winter sets in i'll just have the lights on at night which should provide enough heat. that 20 inch distance thing is a bit of a worry also. height is restricted enough already