The RV solar panels we use are the same kind of panels used on off-grid homes and in other applications for harnessing electrical power from the sun. We recently added to the system on our motorhome.
How many RV solar panels do you need? It depends on your RV, your RVing style, and your electrical usage. It also depends on the weather, what part of the country you are in, and how and where your panels are installed. The age and quality of your panels; the size, type, and efficiency of your inverter; and what you have for batteries and charge controllers are also part of the equation.
We’d been doing okay with our previous solar system. We had been using the motorhome as our primary vehicle; we don't travel with a toad. That meant driving it to the grocery store, out to eat, to the post office and all our daily errands. Driving used the engine alternator to charge both the engine battery and the coach batteries. We watched our electrical usage, and usually went somewhere every day or two. In that situation, we had adequate electricity from our batteries and our inverter.
This summer, we are somewhat stationary for a while. We have a small SUV
here to run our errands. Being settled, we tend to use more electricity
than usual. Without the charge from the motorhome alternator, we seemed
to be somewhat short on electricity on cloudy days. We decided it was
time to invest in some more solar panels for our RV.
we purchased our current motorhome for a single season of use. We
outfitted it with two solar panels we had in storage. We added some
budget panels to help get by last winter while in southern Texas.
We decided to purchase and install additional panels to get our system up to the capacity we need now. After we settled in, and had a good shipping address, I went shopping online.
I checked with my favorite solar suppliers for some deals on panels. Two
of them are RV Solar Electric and Backwoods Solar; both sell quality
products. RV Solar Electric is very helpful and knowledgeable about RV
applications, especially if you don’t know what you need, or how to put
it together on your motorhome. (We got our first RV solar panel package
from them, back in 1991.) Backwoods Solar is more independent living
based, and geared toward larger permanent installations. I’ve done
business with both, trust both, and I feel I either will treat me right.
We originally were looking for 200 watts of new panels. After looking, measuring the roof space, looking, measuring again, refiguring, considering different charge controllers, and going back and forth, we changed our plans. With all that measuring and figuring, we had gone from 200 watts, to 150 watts, to 250 watts, and finally, settled on 300 watts.
We ordered three 100-watt panels. We also chose a 30-ampere charge controller and properly sized wire, all from Backwoods Solar.
Some of the reasons we chose what we did:
• The 100-watt panels fit the space on the roof better than the 150-watt panels.
• The 60-watt or 75-watt panels would have required more mounting hardware and more wire connections to install.
• With the larger charge controller, we can add more panel wattage later without having to upgrade our controller.
• We can move all of our RV solar equipment to a different recreational vehicle at a future time.
Armed with the exact measurements of the solar panels, I searched for aluminum angle iron to build brackets and mounting feet. I found three different suppliers, with greatly varying prices on exactly the same materials. I chose Midwest Steel and Aluminum, out of New Hope, Minnesota. The metal was delivered in just four days, a day before the solar panels arrived.
Wearing gloves and eye protection, I used a circular saw with wide kerf carbide tipped blade to cut the aluminum angle for the frame and feet. I then used a file to smooth the sharp edges. Usually I use 1 1/2 x 1 1/2 angle, but here I used 3 x 3 angle to achieve enough height to go over obstructions on the roof. I used stainless steel mounting bolts and screws from the local hardware store. I ran the wires down the refrigerator vent to eliminate making a hole in the roof. I used self-leveling roof sealant under and around the feet to seal the screw holes and add extra adhesion for the feet. The installation went well, we turned the system on, and everything worked well.
From these 300 watts of panels, we see about 15 amperes peak charging on a typical day. Our charge controller says there are days we’ve charged over 90 amp hours. This is in addition to the electricity we are getting from the panels we had before.
With the long summer days, the panels could be producing more -- they have the capacity to produce more. But, when our batteries are full, the controller does its job and goes into float mode to prevent over charging.
We’re happy with our newest RV solar panels. It continues to amaze me how they sit there benignly, making electricity from the sun.
Coleen's comments: My husband, Bob Nilles, wrote this article about adding more RV solar panels to our motorhome. For more details about the various kinds of panels and our experience using solar power over the years, be sure to read the other articles he's written solar. Having a good solar system, and taking advantage of the "free" electricity from the sun makes a world of difference in our RVing flexibility and freedom.