It's a 100watt red bulb, and it does stay on 24 hours. I'm going to get a 75 watt one tomorrow, though, for I'm afraid it might be getting a bit too hot at times. The hot side stays around 90 degrees, but if my room temperature fluctuates too much it can get to 95 or so. I was gonna pick one up today but was so tired after work that I forgot.