On the left. Yea. It has a red bulb in it that I control with a dimmer, because I like to keep the house cold in summer. Don't worry, he has a UTH controlled with a Lutron Dimmer and his temps and humidity are constantly checked with my Accu-Rite digital thermometer. Currently 93 on the hot side, 82 on the cool side. 37% humidity
I did TONS of research. He's in a 20 long with a hot hide, cool hide, a big one in the middle (which is where he likes to sleep) and a moist hide on the hot side also.
I also have a lamp in my vivs along with the UTH, I only use them during the winter to keep up the air temp on the hot side.
I have taken to using 75w night glow bulbs as I find that some of the geckos don't like the red one and wont come out if its on.