I did a little research into Solar Cells and RVing. This is a non bias review of the issue. I am not involved with sales, installation, boondocking, dry camping, Green Peace or any other environmental cause. I am looking at it from a purely financial and beneficial stand point.
Let start with the size in amps that would be needed for an off the grid RV. If you are frugal with your electric use, leaving the lights off, using propane for heating water and air, limiting your tv and computer time you can probably get by with about 20-30 AMP/H. You have to remember that you have a lot of equipment in the RV that uses electricity even if you aren’t. You smoke, CO2 and Propane detectors, the converter/inverter, the refrigerator (even on gas uses 12 VDC) and water heater all use DC all the time. Then you have fans, lights, electronics that also use AC all of the time. So just to keep the system running I figure you will need from 500 to 600 Watts. Then on top of that you have your entertainment and living wattage. So figure you will need from 800-1000 watts of consistent solar power to meet your needs as a minimum. Now solar panels are only about 6% effiecent. That means that to create that kind of power you will need 15 sq yards of space on the roof or about 6-8 panels, depending on the part of the country and the weather.
Equipment needed is the next area. You need the panels, charge controller, batteries, converter/inverter, monitoring unit, wiring, mounting hardware and the available weight on the RV. So lets talk about weight first. The solar panels are going to weight around 40-50 lbs each with hardware and wiring. The batteries will weigh about 50 lbs each. You will probably have 4-8 6 volt batteries. The controler will weigh in at about 15 lbs. The monitor is 5 lbs. Total added weight to the RV for 8 panels would be about 900 lbs.
Cost for all of this is the real kicker. There are all kinds of prices out there from $200 set up to $6000 or more. Basically you will get what you pay for. A trickle charger setup will not work for boondocking. It is designed to kept the battery charged when not in use. Basically the first panel will run from $800-$1000 plus installation. Each additional panel will be from $600-$750. So you can see that an 8 panel full time off the grid system will probably cost you from $5000 to $6250.
All of this assumes you are living in the desert with no bad weather, that you always have a clear shot of the southern sky and that the panels are mounted to be able to track the sun during most of the day. Which means you will also need a supplemental energy source as well, IE a generator.
I don’t know how long you plan on boondocking, but for the heck of it lets do some math. First off the resale value of a used solar system is non-exsistent. So you won’t recover any of your investment that way. The good news is it should last 20-25 years. The added holes in your roof will probably mean more maintenance and sealant over the years and will affect the resale value of your rig. So unless the buyer is also looking to boondock and wants to take the solar system as well, you will lose money on the RV when you trade it in.
Solar vs Generator? There is no doubt that solar over the long haul will reduce your energy expenses, but by how much? A generator run about a gallon of fuel an hour. If you are using gas that means it cost about $3 an hour to run and you will run it about 3-4 hours a day to keep the batteries charged, so $12 a day. So for the first 416 days or so of boondocking you it will be cheaper to use a generator than installing a $5000 solar system in perfect sunlight. Call it two years before you will see a benefit of using solar over generator as a full time boondocker. If you hook up at a campground at all, then the time extends out even more.
Since we plan on only boondocking a week or so a year once we head West, it was pretty easy for me to see that this wasn’t worth it. You need to decide if it is for you.