What is the difference between the SE U-8 and the Deluxe 8?

Hello Pete, Both heaters require an external control. The Tylo Deluxe heaters can utilize the manual TS 30-01 control. They can also utilize one of the Tylo digital control, but that combination requires a third component, which is a relay box. The Tylo SE heaters will only work with a Tylo Digital control, but have the relay box conveniently built into the heater. Typically, if someone wants a manual control, we recommend the Deluxe heater. If they want a digital control, the SE heater is a more economical setup than using a Deluxe heater with a relay box.