Actually if you are running something like a RHP, you don't "need" belly heat from a UTH. I've had my boa for 2 years since she was about 8 weeks old and I have never used UTH for her. I have her in a 48x23x14 Proline cage with a Pro products RHP on a Herpstat one and she has done perfect, almost too perfect as she is overweight at the moment The flip side is that even with a UTH, you might still need a RHP or CHE as UTH don't heat the ambient air. Now for my 7 week old BP, I do have her on a UTH and CHE but its a temporary tank as I will be getting her either an Animal Plastics or Proline cage in spring when she outgrows her 20 gallon tank and is more settled in. In that case, like my boa, I will probably just run RHP on a Herpstat as well. Regardless though, to beat a dead horse, you need a thermostat or at the least a rheostat for any heat source for a snake.