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Part 1: What is the best solar panel for my RV and how many do I need?

Sunshine on my shoulders makes me happy! Okay, I’ll leave the song references to Mike Sokol, but sunshine can make your house batteries happy and happy batteries mean a happy camper. What I’m talking about is using the power of the sun to charge and condition your batteries using solar panels.

Price vs. quality

There are three types of cells available for manufacturers. Monocrystalline cells are the most durable and most efficient; however, they are the most expensive. Many discount tool stores and home improvement stores sell inexpensive solar panels that typically will not hold up to the abuse they encounter in the RV world. For the past five years, I have worked exclusively with Zamp Solar (now owned by Dometic) and Go Power! and have had great success. All the products we have installed are still working as designed. They are easy to install, use high-quality materials, and if a cell does get compromised, it doesn’t shut down the whole panel. There are some other good products out in the market, so enough of the commercial!

Here is how a solar panel works:

The solar panel catches the sun’s rays and converts them to DC charging power, similar to a filling station providing fuel. This fuel travels through a solar controller that monitors the amount of fuel in the battery and will shut off when the batteries are charged properly. A controller is important as a consistent charge to the batteries can overcharge or “boil” them and cause damage. This is a similar procedure the shoreline cord provides when plugged into a campground source as it travels through the converter and charges the batteries. If you want to get more technical into how the photons knock the electrons from the atoms and allow the flow of energy, click here.

The basics are this: Your house batteries simply store energy known as amp-hours, which run 12-volt DC components such as interior lights, roof vent fans, water pumps, and any LP devices such as refrigerators, stovetops, water heaters, and furnaces. As your battery is drained of amp hours, you will need to replenish them with either shoreline power or generator through the converter/charger or with a solar panel system. If you are boondocking or dry camping, you will need to either run a generator for long periods of time, or have a solar panel system.

What will my solar panels run?

Technically nothing! The solar panels only provide a charge to the batteries. The house batteries provide 12-volt deep cycle power for the components in your rig.

What size and how many panels do I need?

Solar panel technology has changed dramatically. The newer panels are lighter, smaller, more powerful, and more affordable. There are several sizes to choose from depending on your needs from small backpack-sized ones to larger 190-watt panels that can be combined to provide 570 watts of charging power!

To determine the size of panels and how many are needed for your rig you have to determine your amp draw needs. First, you need to identify the components that run on DC and how long you will use them in a day. Here is a chart with some common components and amp draws:

12-Volt amp draw:

  • Incandescent Lights: 1.5 amps
  • Halogen Lights: 1 amp
  • LED Lights: 0.12 amp
  • Smoke Alarm: 1 amp
  • CO Detector: 1 amp
  • LP Leak Detector: 1 amp
  • Furnace: 10-12 amps
  • Water Pump: 5 amps
  • Refrigerator on LP Mode: 2-3 amps
  • Stovetop: 1 amp
  • Roof Vent: 3 amps

Note: If you have a residential refrigerator and run it through an inverter, this will deplete your batteries quickly!

What’s the calculation?

The next step is to multiply your total daily hours by the number of days you are going to be out and compare that to the amp hours your battery or batteries can provide.

The challenge most of us will have is trying to figure out how much and how long we are actually going to be using these items. It will change with the ambient temperature, how many people we take on a trip, and other factors. Go Power! has a very sophisticated calculator that you can download here.

Another good place to start is this simple chart provided by Zamp Solar:

How many panels and how big?

So, back to the question: How many panels do I need and how big/wattage? One group 24 deep cycle battery is rated at approximately 80-100 amp hours; however, you can only drain a lead-acid battery and AGM down to about 50 percent, so that means 40-50 amp-hours. A typical RVer could draw 1/3 usable amp-hours per day or more. A 100-watt solar panel can generate 5.5 amps per hour in full exposure, which means it could keep up in this situation if you get a full 6 hours of exposure. By the way, this comes from Dakota at Zamp Solar, who answers the phone every time I call and knows the product as good or better than the others I’ve talked to. I would highly recommend talking with him if you have questions!

But there are several other variables to consider, too, such as weather, temperature, and battery condition. Severe weather means RV owners are inside the rig more often and using components that draw more battery power. Plus, this generally means less exposure to the sun. Extreme high temperatures mean appliances such as the refrigerator run more often, and vent fans are running, which means more 12-volt power draw as well as the furnace in low temperatures. “Typical” usage in an RV is hard to calculate! Keep in mind, you can start with one or two panels and if that is not keeping up a charge, you can easily add more.

Read part two

Related:

Zamp Solar products on Amazon

Go Power! products on Amazon

##RVT1010

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chris
2 months ago

“A 100-watt solar panel can generate 5.5 amps per hour in full exposure..”

I see the author is using this incorrect term.

Roger H.
2 months ago

Newbie question, Are the amp draws listed above per hour or 24 hr usage? Great article.

chris
2 months ago
Reply to  Roger H.

‘Amps per hour’ is a term I hear often, but it’s incorrect. Amps is the same whether it’s for one second or one hour because amperage is an instantaneous measure of current. If you draw 10 amps for 1 hour, that’s 10 amp-hours, but perhaps some people like to say ’10 amps per hour.’

Voltage is also an instantaneous measure of pressure, so when you turn something on, it’s at 12v right now, drawing the number of amps shown above. So far I’ve never heard anyone say “volts per hour.” 🙂 Clear as mud?

Last edited 2 months ago by chris
Roger H.
2 months ago
Reply to  chris

Yup, thanks for your quick response. I have a lot to learn about solar before we order the retirement 5ver once the COVID thing eases up ?

Dr. Michael
2 months ago

Does anyone have feedback or thoughts on portable solar panels (like from Renogy, 200 Watt Eclipse Monocrystalline Solar Suitcase | Renogy Solar) that could solve the problem really easily?

chris
2 months ago
Reply to  Dr. Michael

Portables are ok, but kind of a pain to move around or pack if you use them very often. And then there’s wind…

Last edited 2 months ago by chris
rvgrandma
2 months ago
Reply to  Dr. Michael

If you go to cheaprvliving channel in youtube, Bob Wells has some excellent videos on solar for boondockers. Might help you. He favors both portable and on roof. If you want to park in the shade you need portable to capture the sunlight. He also love Renogy.

Dave Solberg
2 months ago
Reply to  Dr. Michael

Dr. Michael, I do cover portables in part 2 as well as batteries and other items which I should have referenced at the end of part 1. Check out the article tomorrow and let me know if you have questions after that. Thanks

Charlie from Denver
2 months ago

Dave, I liked your lead in, but felt that it did not go deep enough. We started with an 100 AH AGM battery from Battery’s Plus along with a solar regulator and inverter from Harbor Freight. Neither was up to managing our light usage. Met a battery/solar wizard in Northern CA and replaced the original install with 100 Amp HOUR (not watt hour) Lithium IRON (not ion) Phosphate Battery – LiFePO4, a PURE SINE INVERTER (not modified Sine) and a 200 Watt Solar collector.

No more problems in spite of running both a 5 cup coffee pot and microwave which barely put a dent in the battery. We will start cooking with an induction cooktop on our next trip. Stay tuned.

Dave Solberg
2 months ago

Charlie, thanks for the comments and what you are using. I do go into a little more detail in part 2 which I should have referenced at the end of part 1. Keep the comments coming!

Bob M
2 months ago

It would be nice to know what the total cost of putting solar on an RV is. I won’t have anything to do with a Dometic product.

chris
2 months ago
Reply to  Bob M

It’s cheaper now than it’s been in a long time. If you can do the work yourself, maybe $600 for the panels, but then there’s the batteries and inverter.

Last edited 2 months ago by chris
Dave Solberg
2 months ago
Reply to  Bob M

Bob,
Check out part 2 as we show how we installed a 100 w panel on the roof of a Class A motorhome so you might be able to do it yourself. It’s difficult to provide cost estimates for installing solar panels in an article like this as there are so many variables such as is your rig prewired for solar which would save an enormous amount of labor time, how many panels are required and the size, different charge controllers, and if an inverter is part of the system? Hopefully part 2 will give you an idea of what you might need for your RV situation and then you can get a better cost projection?

Wally
2 months ago

Nice work Dave. This will be invaluable to those new to solar and a good refresher for some of those who have a little more experience.

Dean
2 months ago

Very good article, excellent simple breakdown for anyone getting into solar. Thanks for the information. When newbies ask me about my solar and I try and answer their questions they soon glaze over (most likely due to my lack of simple explanation) my plan is now to reference this article to them and that should make it easier for me and provide them with easy understanding for their solar interest.

chris
2 months ago
Reply to  Dean

Invariably their first question is “what does it run.”? My experience with newbies asking me questions is that they end up doing all the talking.

Last edited 2 months ago by chris
Dave Solberg
2 months ago
Reply to  Dean

Thanks Dean, I know how hard it is to explain solar power when asked if you don’t have some photos and graphics! It’s like doing a hand puppet show! Let me know what you think of part 2. I know there is more that could be added but there is a fine line about how deep you can go and how long readers will go with you.

David Telenko
2 months ago

Good article for getting started, looking forward to future ones, especially the actual setting up & choosing the right controller, etc.
Snoopy

Dave Solberg
2 months ago
Reply to  David Telenko

David, thanks and please give comments on part 2. I did go into the installation of the unit on the roof, but did not go into the right controller as both Zamp and Go Power are great at not only matching the right controller with the solar panel or panels so this is usually covered during the purchase. Let me know your comments tomorrow after part 2.

Thanks again

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