RV 101: FAQs about RV Solar Power Systems

Right now, solar power is basking in the limelight. “It’ll charge your batteries for free,” says the salesman, “and allow you to boondock anywhere you want!”

The highlights are legion: Solar power is green. It’s available anywhere. Many RVs come “solar-prepped.” It’ll pay for your kid’s college and cook your breakfast, besides.

But what’s the secret truth about RV solar power? Is it really everything it’s cracked up to be?

Let’s shed some light on it.

(Sorry, I couldn’t resist.)

How Do RV Solar Panels Work?

RV rigid solar panel mounted on the roof of a Class B van

At bare minimum, a portable solar power system consists of three main components:

  • Solar panel[s]: Generates electrical energy
  • Charge controller: Regulates electrical energy
  • Battery: Stores electrical energy

Wiring and protective equipment connect these components.

Solar panels capture the sun’s energy, which is then transferred to batteries for storage. Thecharge controller is used to prevent the batteries from overcharging.

Many people also use an inverter to provide AC power for common appliances. An inverter changes the battery’s direct-current (DC) electricity to alternating-current (AC) electricity, which is the type used for residential appliances like air conditioners and microwave ovens.

How Much Does Solar Power Cost?

It’s every engineer’s favorite saying: Let’s run some numbers!

But first, some excuses.

Solar prices have dropped like a rock in the past 5-10 years. Panels cost a fraction of what they used to. However, prices seem to be leveling off.

You can get a decent rigid or semi-flexible 100-watt solar panel for around $100 new.

Now, how about the cost of the entire system? You know what’s coming …

It depends.

On the one hand, you can buy the whole kit-and-caboodle 100W RV solar power starter kit from Renogy for about $300. You supply some of your own wiring and components, which would cost at least another $100. And after a long afternoon’s work, wallah! – you have solar power!

However, a system this size can do little more than top off your batteries to run your common 12V appliances, like lights and ceiling fans.

On the other hand, if you want to run your refrigerator and microwave off your house batteries, then you’ll need three or four $1000 LiFePO4 batteries, a $2,000 3,000-watt pure sine wave inverter, $600 in wiring and protective components, a $200 MPPT controller … and we haven’t even got to the panels …

You get the picture. A functioning solar power system ranges from $500 to $15,000!

Personally, if you’re new to solar, I recommend a solar suitcase. These are all-in-one portable solar power packages that either plug into a solar plug-in or are attached directly to a battery. You can be out the door for less than $300!

Why Aren’t Solar Panels Standard on RVs?

Great question! More and more, they are! RV manufacturers are responding to the needs and desires of the modern customer, who wants the freedom to camp away from a developed campground.

Many RVs can be ordered with 100W and 200W solar panel systems. Some packages are installed at the factory; others are installed at the dealership.

Many RVs don’t come with a full solar power system. Instead, they come with a “solar-prep” package – but beware! That term may not mean what you think it means!

Can I Attach a Solar Panel Directly to a Battery?

You could … but only once. The output voltage of a solar panel fluctuates with the intensity and angle of sunlight. In direct sun, a solar panel could output 18 volts or more!

That’s waaaaaay too much pressure for a 12V battery. That’s like drinking from a fire hose. Batteries are demanding little things, and they must be charged with the correct voltage algorithm. Excessive voltage will cause your electrolyte to boil, which will quickly “fry” your battery, or worse, cause an explosion!

Or you might encounter the opposite problem: too little voltage. You can push 3V towards a battery all day long, and nothing will happen. It’s like trying to smash a rock with a paperclip. You need more brute electrical power to get the electrons moving. So all that solar energy is just going to waste.

A solar controller regulates the voltage from the solar panel. It’s the voltage gatekeeper. Without it, your battery is subject to the whims of sunlight.

Can I Run My Entire RV Off Solar?

Ehh …no. Not most people, anyway. This is a common misconception.

Solar power does not replace any component on your RV. It’s supplementary. It frees you from the tether of the electrical grid and allows you boondock, dry camp or Wallydock.

More accurately, solar panels recharge your house batteries, which you can use to power (most of) your RV.

Can I Run My RV A/C on Solar Power?

No. Not directly, anyway.

Consider the power consumption of an air conditioner: You’ll need about 600 Ah per day to run an A/C, and a typical battery provides around 70-90 Ah. You’d need 6 deep-cycle batteries and a lot of panels just to power your refrigerator, and that’s not factoring in all the other appliances. And you’ll need a soft-start capacitor. And an inverter. And somewhere to store all this stuff.

How Many Solar Panels Do I Need For My RV?

This depends on how many appliances you run on a daily basis, as well as what type of battery you’re using.

Let’s give a simple breakdown of required panels by usage:

  • 100 watts: Supplementary use only
  • 200 watts: Light use (lights, fans, basic electronics)
  • 400-600 watts: Moderate use (all of the above plus common appliances such as coffee maker, blender, television, crock pot – but only one at a time!)
  • 1000+ watts: Heavy use (all of the above, set up to work even in cloudy weather or in the shade.)

Do Solar Panels Work When There’s No Sun?

Solar panels will work on cloudy days, but the amount of energy they produce is reduced drastically. For a partially cloudy day, power output can be reduced by 30-50%, and a very cloudy day may provide you with only 10% of your normal output.

Solar panels respond to the intensity and angle of the sunlight. So direct sunlight in November will generate less “juice” than direct sunlight in July.

How Should I Clean Solar Panels?

You should clean solar panels for two reasons:

  1. Increase energy efficiency
  2. Prolong lifespan

Dirty solar panels more easily overheat, which shortens the lifespan.

Spraying with water will work well enough in most cases. If there is heavy buildup that requires additional cleaning, mild soapy water, and a non-abrasive cloth or squeegee works best. Please consulate your manufacturer’s guidance.

Is Solar Power Better than a Generator?

This is not an either-or-preposition. Many campers use both quite happily.

I did take a poll of some real RV campers, though, and I heard some interesting thoughts on this versus question. If you want to know what people think of solar power vs. generator, check out this article.

Which Kind of Solar Panel Is Better: Rigid or Flexible?

Flexible panels have a few advantages over rigid panels. They’re lighter, can conform to curved surfaces, and still provide you with the same amount of power as a rigid panel.

However, they typically cost up to twice as much as rigid panels, which can add up if you’re planning a solar system with six or more panels.

Historically, rigid panels tend to last longer. If you demand maximum durability, rigid panels are your best choice.

Best to leave the flexible panels for curved roof applications where rigid panels are not an option.

Psst … You should consider the mounting solution carefully! Structural double-sided tape is commonly used to attach panels to RV roofs, but removing the panel will likely damage or ruin it completely.

Which Kind of Solar Panel Is Better: Onboard or Portable

Each type of panel has its own advantages.

Onboard panels are more rigid, and they stay affixed to the top of your RV. They are a bit more durable, and they can charge while you’re driving.

Portable panels need to be set up every time you stop, but they have the advantage of (you guessed it) portability! Place them in the sun while your RV sits 15 feet away in the shade. When you’re camping on a 95-degree summer day, you’ll be glad you packed your “solar suitcase”!

Is It Better To Use High-Voltage Panels?

This is more of an advertising gimmick than actual fact.

There are true “high-voltage” solar panels designed for grid tie-in. These are the ginormous panels you see on solar farms and large solar arrays.

Most solar panels designed for RV use has a Vmp rating of around 17.5-18 volts. They are intended to be used with an industry-standard PWM controller.

“Higher voltage” solar panels don’t do anything to charge your batteries faster or better.

What Kind of Battery Should I Use For My RV Solar System?

You have three main choices here; Lithium, flooded lead-acid, or AGM.

  • Lithium batteries are the most expensive, but allow you to utilize almost 100% of the battery before requiring a recharge, meaning you also get more bang for your buck.
  • Flooded lead-acid batteries is the cheapest option, but they are also the most likely to need maintenance.
  • AGM batteries have a cheaper initial cost than lithium, but don’t last as long, making them more expensive in the long run. They also shouldn’t be discharged past 50% before you recharge them.

How Long Will Solar Panels Last?

Solar panels can outlast your RV if you take care of them! Most panels have an average warranty lifespan of 25-30 years, with no maintenance besides cleaning required. However, the warranty reimbursement value is generally prorated.

What Is The Maintenance Cost For RV Solar?

One of the best things about solar power is that very little maintenance beyond basic cleaning and inspection is required. And best of all, solar panels are recyclable! The maintenance costs are really limited to when your batteries or charge controller wear out.

Are Adjustable-Angle Panels Worth It?

For most people, the additional cost and trouble of installing a tilting amount is not worth it. It’s not like your Rv faces the same direction all the time, does it?

However, if you have limited space and want to make the most of your panels, tilting panels can boost your power input by 10-15%.

If you’re long-term camping, then you might consider mounting your panels on a tilted base, too.

Can Solar Panels Be Damaged By Hail or Lighting?

Solar panels are made out of the same tempered glass that makes up auto windshields, so it is very rare for them to be damaged by hail.

Lightning damage is rare, but it can happen. Typically it is the frame or connected electrical devices, not the panels themselves, that are susceptible.

There are lightning protection systems that can be purchased, and it’s always a good idea to use surge protectors for your electronics. Surge protectors protect your RV’s electrical system from voltage spikes caused by nearby, but not direct, lightning strikes.

If you are unlucky enough to have your RV directly struck by lightning, then I hope you have insurance.

How Can I Determine The Amount of Power I Need?

The guide above should give you a general idea of how many panels you’ll need. To check actual consumption, your best bet is to take a trip for a couple days and see how much power you actually use. Use a battery monitor over these days to see what your daily power consumption is, and then choose a solar system that will meet these needs.

Is RV Solar Worth It?

If you like the idea of a noise-free supplementary power source that is also environmentally friendly, then solar is definitely a worthwhile investment.

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