Used our Roo this past weekend with overnight lows in the low 20s, maybe high teens one night. I run an electric heater that can be adjusted on both 750 and 1500 watt settings. I can run it full on the 750 setting. Maybe 1/2 to 3/4 on the 1500. Problem is, the interior outlets are on the same circuit. I plug the heater into the outlet next to the fridge. Unfortunately, the bed heaters are all on the same circuit so I've been known to trip a breaker every once and a while. Almost ran a separate cord from the post, but the furnace made up for the electric heater's lower setting. Really want to add a dedicated 15 amp breaker for heater use. Figured I'd put it next to the other one by the fridge. Only a foot or two of Romex needed. Hope it's doable. Hope this info helps some.
2011 Rockwood Roo 233S
2008 Chevy Express 3500 Explorer Conversion
Prodigy Brake Controller