RV Solar Systems – Sizing your system.

RV solar
Roof mounted solar panels

Before Lynda and I retired our RVing/camping experiences were limited to long weekends and a two or three-week vacation once a year.

Our RVs were equipped with a generator or we brought one along  to recharge the RV batteries. Solar power didn't enter my mind, of course, it was almost unheard of back then.

The tradition of using a generator continued after we retired and began spending more time traveling in our RV. It didn't take long for us to realize we needed to consider Solar Power.

The constant drone of the generator was irritating and I am sure our neighbors were irritated as well. Sometimes it would be difficult to start and I would forget to fill the gas tank and it would quit while we were watching TV, and out into the night I trek to refill the fuel tank. The fumes were also an issue drifting by occasionally……. not nice…………. it was time to check out solar.

Exhaust emissions

Small engine smoke

Of course, a solar charging system gives off zero emissions, but what about your generator?  Small engines are becoming a very real pollution problem.

It is a little known fact that a small engine can emit as much pollution as a full-size car.This is why governments are creating legislation to demand emission standards for small engines.

For this reason alone all of us should seriously consider an RV solar system.

The Plunge

I have always been curious and excited about new technologies, especially the ones that can save money. On one of our first RV tours, I had a conversation with a fellow retired RVer about his RV solar system and the fact that he had never plugged into a power source since he had his system installed was intriguing.

That was enough for me, I bought our first 60-watt solar panel kit  for our second spring trip to the southwest desert. The kit contained the solar panel and a charge controller. I had no idea how it would work or if it would be adequate for our needs, it was definitely an experiment.cropped-DSC01993.jpg

We headed for the desert. After arriving and setting up camp, I assembled the solar charging kit and connected it directly to our 2 –12-volt deep cycle batteries.

I soon realized that the 60-watt panel only slowed the discharge of our RV batteries. I ordered our second 80-watt panel. A do-it-yourself kit. I built it on our next trip south while we were camped in the desert. It was a satisfying accomplishment and it actually produced electricity.

Volt meter
Typical voltmeter

After a couple of days, I checked our batteries with a voltmeter they were still discharging although much slower than with just the 60-watt solar panel. We needed more solar panels.

On a subsequent trip to the central water source to replenish our fresh water, I chatted with another camper and the subject of solar power came up. I explained that I needed at least one more panel to boost the output enough to charge my batteries. The fellow said I should try Sun Electronics.

I made a mental note, googled the name back at our RV and checked out their solar panels. I ordered an 80-watt panel for $150 I almost crapped myself, I had paid $300 for the do-it-yourself kit………and a day's labor. No regrets though it was a good education.

The panel was delivered to Quartzsite, Az a few miles from where we were camped. We now have 190 watts comprised of 3 solar panels that I set on the ground and move a couple of times during the day to keep them focused on the sun.

Finally, the system was complete.  It fully charged our 2 – 6-volt deep cycle batteries and provides enough power to enjoy the evenings without running out of power.

My Simple Setup

Our set up, 1000watt inverter and 25 amp charge controller

My system is connected directly to my batteries. The 3 solar panels are connected to the charge controller, which is connected to the batteries. The inverter is connected to the batteries as well. I run an extension cord or two through a window of our trailer and from there we plug in the appliances we want to use.

I know this setup is a bit cumbersome, but if I put my solar panels on the roof I will need at least one more panel and run the wires through the fridge vent. The only issue I have with this setup is I need room to store the system for traveling.

Dry Camping………… Perfect

Power wise we had become totally independent, no need to hook up to electricity or run the noisy smelly generator. We are able to use most of our appliances in our 36' travel trailer except the air conditioner and microwave. There is even enough power to run the furnace for an hour or so on a chilly morning.

Along with using the lights and water pump, we watch satellite TV for about 3 hours in the evening, surf the net, keep our electrical devices charged and Lynda even quilts using her sewing machine, and a small iron.

We are off the grid………… wow what a feeling.

We are careful with our power as well as fresh water and black and gray, but we sure don't suffer. Now that we have solar power to recharge our batteries,  a water bladder for transporting fresh water, and the blue boy tank for the sewer. Life is great boondocking. For these and other boondocking ideas, Check out my previous article.

RV solar system
Solar Panels on a tripod stand

Solar Power is probably one of the greatest discoveries of our time. All RVs should come equipped with a solar charging system large enough to enable dry camping.

Even if you are not into dry camping and only stay in campgrounds or RV parks, an RV  solar charging system will reduce your electrical usage, thereby reducing your power bill (most RV parks charge extra for electricity when staying for more than a couple of weeks).

The only time we have a problem with our solar system is if the sky is overcast for a full day with no sunshine to charge our RV batteries, that's when the backup generator is necessary.

 System Sizing by Actual Use

There are many ways to calculate what size of solar system will meet your needs. Some are quite involved mathematically, some utilize an accumulating amp-hour meter, and some are basically "rules of thumb".

The actual USE method works well.

To use this method go boondocking in your RV (without running your generator or plugging into shore power) for as long as it takes to run your batteries down. Use electrical appliances as you would normally while camping . This will indicate how much power you consume on an average day.

You can use a simple voltmeter to check your batteries. A fully charged 12 volt battery depending its age should register 13 to 14 volts. A discharged battery will read 11.5 volts or less. 

Check out my previous article on RV Batteries 

Let's say you were able to "boondock" for two days before you noticed your batteries getting weak. Now you can figure out how much power you used.

Deep cycle Battery

  • First you need  to determine the storage capacity of your batteries. Let's say you have two (2) relatively new deep cycle batteries that are rated at 100 amp-hours of storage each. This means you theoretically have 200 amp-hours of energy to draw on (2 x 100 = 200). However, only about 80% of that is usable so you really only have 160 amp-hours of energy to draw on (0.8 x 200 = 160).
  • Now divide 160 amp-hours of storage by 2 days = 80 amp-hours of energy consumed on an average day.
  • Now we need to determine how many solar panels you will need to replace that 80 amp-hours of energy you consume per day. We will assume that you use you RV during the sunnier half of the year and/or you follow the sun south during the darker half of the year. This will give you an average of five (5) "peak sun hours" per day.
  • A 100-watt panel produces an average of about 6 amps per peak sun hour, or about 30 amp-hours per day. 6 amps X 5 peak hour = 30 amps.
  • Given the above example, you would need three 100 watt solar panels to fully recharge on the average day. 30 amps X 3 panels = 90 amps, and you used 80 amps.
 My research indicates that most RVers consume between 75 and 150 amp-hours of energy per day depending on their lifestyles and degree of frugality. Which means that some people will only get about one day of boondocking out of the batteries used in the above example. These folks would need three to five 100 watt panels in order to fully recharge their batteries daily.
A Battery Monitor

A more technical approach would be to purchase and install a battery monitor before you go boondocking. These devices record your consumption and give you a reading that tells you how many amp-hours were removed from your batteries. This means there will be no guess work or mental math. You will know what you used and then make an informed decision on what size system you will need to meet your lifestyle.

 My Solar Power Experience
After starting with a small solar kit of 60 watts of solar panels we have graduated to about 200 watts of panels, a 25 amp. charge controller and 2 – 6 volt batteries. I set the panels on the ground in a tripod shape facing the sun. I move the panels a couple times during the day to keep them focused on the sun.
In my opinion a good quality 12 volt or 2-6 volt batteries, a 25 amp charge controller, 400 watts of solar panels and a 1500 watt inverter will meet the needs of the average RVer.
This is at the very least a good starting point, and if you find that this system is not quite enough it is easy to add more panels and even more batteries and a larger inverter.
Wet batteries, (batteries with acid) need to have the level of acid checked regularly and topped up with distilled water after charging.

If you would like more information on do-it-yourself RV solar systems order this book.

 This solar kit comes with everything you need, 4 x 100 watt panels, charge controller, and all the mounting hardware. Some of the reviews suggest more wire may be needed depending on your installation method. The only item left to complete your system is an inverter. I have picked one that will work with this system, check it out below.

This 2000 watt pure sine wave inverter will work well with the above 400 watt solar system. Pure sine wave works well with sensitive electronics.

My thought has always been that if you spend about a month boondocking you have paid for your system. Multiply an average of $30 per night in an RV park times 30 nights = $900 + tax.

I have included this do-it-yourself video if you want to install your RV solar charging system on the roof of your RV.

Gord B.

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For your convenience I have compiled a comprehensive list of equipment and items you may need for your RV and camping travels, complete with product  links, click here to check out my list & links.

Now you are ready to boondock, dry camp, live off the grid, get away from the crowds, save money and help save our planet.


3 thoughts on “RV Solar Systems – Sizing your system.”

    1. The air conditioner will run off and inverter but it will need to be about a 7000 watts and then your batteries will deplete quickly, not very practicle for an RV. If you need your air conditioner a 4000watt generator would be the way to go. An inverter will supply alternating current for your outlets if wired to your system. I hope this helps.
      Thanks for your comment Gord

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