In the most simplest form, solar is just a fancy battery charger that harnesses the suns energy to charge your batteries. Technically anything you run off your solar is really running off your batteries first and solar is there to recharge them.
This answer really depends on a lot of factors that I can talk through with you to personalize your system to meet your needs, but generally speaking the actual solar panels are not the main expense of your system. Most people also never complain about having too much solar, but it’s still good to have a balanced system with good battery storage to meet your needs and enough solar to recharge those batteries. Other factors depend on if you are trying to use solar only with no generator or if you don’t mind supplementing your charging with a generator occasionally. A really basic rule of thumb is about 2w of solar for every ah of battery storage. With Lithium batteries this can be closer to 3:1 or more. A lot of people forget that in the winter flat solar panels can have a reduced output of 50% or more plus the shorter days, so if you full time, it’s best to plan for worst case scenario.
Your RV has 2 distinct power systems, it has a 12v power system powered by the battery and 120v system that uses shore power or generator to run. The heart of your RV is ran by 12v power and this is why battery power is so important. Even though you have many appliances that run on propane, they have a control board that uses 12v power to operate (RV fridge, furnace, water heater). Without 12v power, these items won’t run. Other 12v items in your RV include most lights, water pump, furnace fan, max/fantastic fans, safety devices (CO2/propane), slides & jacks. The slides and jacks are big draws of 12v power so a weak battery can play havoc with them.
On the 120v side are all the plugs like you find in a house. In most stock RV’s these only operate while hooked to shore power, or running a generator. You might even have some 120v lights.
Most RV’s come from the factory with a converter built in. The converter’s main purpose is to convert 120v AC power to 12v DC power. This allows your batteries to charge while plugged in or generator is running, and to provide 12v power during that time to cover the 12v loads without draining your batteries. If your batteries drain down while plugged in, usually it’s an issue with your converter.
An Inverter does the opposite and converts 12v DC power to 120v AC power. Usually your RV does not come with an inverter unless it had a residential fridge from the factory. Then it may have a small inverter to run that and/or a couple plugs. Some high end rigs do come from the factor with inverters installed. An Inverter is what allows your 120v plugs to work while not hooked to shore power. However, you have to be careful how much power you are drawing as high draw items can deplete your batteries very quickly.
Most RV’s usually come with a 4-5 LED light system that tells you how charged your batteries are. Although this gives you a range, it’s a guess based on voltage and really not very accurate. A battery monitor with a shunt is a device that accurately measures the amps that travel into and out of your batteries. With a known battery capacity, it’s able to accurately record how many amps from full you are. It’s the only accurate way to know the true State of Charge (SOC) of your batteries. Think of a battery monitor like a fuel gauge in your car. It tells you when your car is full and lets you know when it’s empty or anywhere in between. Although it’s possible to maybe judge how much fuel you have left by the miles you have traveled, it’s a guess at best and doesn’t take into account your actual fuel mileage. A battery monitor does the same thing and takes the guess work out of knowing your true SOC.
A solar consultant listens to your needs and helps you design a system that will meet your needs and budget. The main reason to hire me as your solar consultant is I have the expertise of living off grid with various size systems and having designed and built many systems, I have a good idea of what you will need to be happy with your system.