I’m an atypical RVer; we never plug in or hook up. No generator. It seemed to go well from day 1 in 2008 when we bought a former rental class C. However, on our first long trip the heater suddenly stopped working - dead batteries. I had been using the voltage method of monitoring the batteries, idiot lights and voltmeter. They are very optimistic, indicating nearly full charge with charging from the engine and for hours after charging. I bought two new deep cycle 12 volt batteries at $90 Canadian each. Luckily there had been some posts about inexpensive battery monitors here so I got one of these
Ebay bargainThe new set of batteries lasted well as we stopped using them after 50% discharge. This was a bit tough but we had all LED lights, no invertor so couldn’t use the microwave and liked cool sleeping so the heater was only used in the morning. I also worked on the engine charging system, eliminating a drop of 1.5 volts from engine battery to house batteries which had made that charging ineffective.
Step 2 was getting a solar panel. Just one, 100 watts from Renogy with charge controller, via Amazon for $200 Canadian. Most people need more but 100 watts is more than adequate for us using just the heater, water pump, fridge on propane (2004 model with no defrost feature), and charging the usual phones and tablets. The batteries have never gone below 80% charge since getting the solar panel!