im using 2 1000 watt lights and a 600 watt in a 6 x 10 room and keep my room right at 81 deg. far. and never have a prob. and i got friends that use 6 1000 watts in a 10 x 10 room and love it. and if your using 1 1000 watt in a 10x10 room weather it is full or not your still losing light to room...