Interesting data. Burn rate is higher than expected. Do you notice much difference in consumption between 32F and 0F?Here is a data point from our composite panel camper. During our winter travels, the Webasto ThermoTop burns around a litre of fuel every 2 1/2 hours. Since it can be running 18+ hours a day, (that is, when not driving and using the engine hydronic circuit) that consumption is significant enough to factor into our range calculations. I had OEV seal up a small pass-through into the cab to eliminate one hole in the envelope but then we need to keep some cross-ventilation for air quality.