I think an energy audit is a worthwhile exercise. I haven't really done one on my coach, but the highest draw we have is the forced air furnace. We had 300w of solar installed with a 30a PWM controller on factory "solar ready" wiring charging two 6v batteries.....barely worked. The I upped it to four 6v, added another 150w panel, moved the controller down to the pass thru closer to batteries and increased the wire from the panels to the controller to #4. Now I have all the power I need. Incidently, we don't have an inverter to run anything 120v/AC. We are all 12v and propane. Never run a genny either. Someday I will upgrade to an MPPT so I'm getting all that the solar is harvesting........but really for us it works good enough like it is to spend the $$$ somewhere else.