Solar Tutorial Part I – Understanding the Basics of RV & Marine Solar Power

This page is the first in a series of four posts that explain the nitty gritty details of RV (and sailboat) solar power. The intention is to demystify the subject of marine and RV solar power and make it understandable for all, regardless of how technical you are or how much you know about electricity. The pages are linked together with arrows at the bottom of each page.

Since we started traveling full-time in 2007, we have been living almost exclusively on solar power, first in a travel trailer, then a fifth wheel trailer and also in a sailboat.  We don’t stay in RV parks or campgrounds or marinas, and on the rare occasions that we do, we don’t hook up to shore power.  As of June 2019, we’ve spent over 4,000 nights living off the grid without electrical hookups in our rolling and floating homes.

A solar power installation in an RV gives you the freedom to have full electrical power anywhere and at any time: at a rest area, in a parking lot, or at a National Forest campground.  Likewise on a boat, you can anchor out for an unlimited time in bays and coves.  Solar power runs without using any gas, is silent, doesn’t smell, and doesn’t require any setup (those shore power cords are mighty ungainly).  Although we do have a gas generator in our trailer, we use it only when we want to run our 15,000 btu air conditioner, not for charging the batteries.  It is a Yamaha 2400i.

Wrapping your brain around solar power for a rolling or floating home can be confusing, but it is actually quite straight forward.  Here’s the whole thing in a nutshell (wherever it says “RV” you can also think “sailboat,” as the principles are the same).

RV Solar power instalation on a fifth wheel trailer

Mark finishes three days of installing our fifth wheel’s solar power system while boondocked in Flagstaff, AZ.

There are 2 functions that your rig needs to have if you want to live without electrical hookups:  

  •  A system to charge the batteries
  •  A system to create AC power for the rig so you can watch TV and use a vacuum

There are 3 components (or “parts”) used in an RV solar power installation to accomplish the two objectives listed above:

Now put it all together…

  1. To charge the batteries you need:  Solar Panels and a Charge Controller
  2. To use your batteries to generate AC power for your TV, computer, etc., you need:  An Inverter

That’s it!!   Very simple.  To flush it all out a little, here it is in more depth:

Solar Power Function #1 – Charging the Batteries

When an RV comes from the dealership, it usually has either a Converter or an Inverter/Charger in it so it can charge the batteries when it is plugged into shore power (via “hookups” or gas generator).  Converters are cheaper and are factory installed on most trailers.  Inverter/Chargers are expensive (because they are dual-purpose, see below) and are factory installed on higher-end motorhomes.

These appliances take the AC power coming in from the external source (hookups/generator) and use it to charge the batteries.  They usually have a 3-stage charge cycle that charges the batteries quickly at first and then drops to a trickle charge once the batteries are close to fully charged.

morningstar sunsaver 10 charge controller

A $45 charge controller for a small solar power installation

How do you charge the batteries when you don’t have shore power?  That is where solar power comes in.

When you install a solar power system in an RV, you add two things:  Solar Panels and a Charge Controller.  The solar panels are installed on the roof and they gather energy from the sun and pump it down to the charge controller.  The charge controller keeps an eye on the batteries and takes only as much power coming from the solar panels as the batteries can handle.

Outback Flex 60 MPPT Charge Controller

A $500 charge controller for a big solar power installation

Early in the day, the batteries are hungry and the charge controller passes everything it can to the batteries.  As the day wears on, the batteries become more fully charged and require less and less power.  By afternoon, if the system is sized right for the way the RV is being used, the batteries throw up their hands and say, “No More!!” and the charge controller puts them into “Float” mode, a fancy term for a trickle charge.

None of this has anything to do with running your TV or computer.  It is only about charging the batteries up after they become depleted from use the night before.

The solar panels will charge the batteries no matter where your RV is parked.  If you are out hiking, or shopping at Walmart, or taking a nap inside, the batteries will be getting charged all day long.  If you are at an RV park or marina with metered electricity, you can save a few dollars by not plugging in!!

If you park under a tree, and the panels are shaded, you will get dramatically less power from the sun.  A tiny bit of shade results in a huge decrease in how much the charge the batteries can get.  We always park in full sun.

Sailboats have a terrible time with unwanted shade from the mast and boom.  When at anchor, pulling the boom over with the traveler and forcing it further out with a preventer helps a lot, but the mast is always a problem when the sun comes from forward of the beam.  If you are sailing and heeled away from the sun or the panels are shaded by the sails, too bad!!  So, on a sailboat, install more solar panels (more total watts) than you think you’ll need!

100 watt portable inverter from Walmart

A 100 watt portable inverter ($15). Plugs into a cigarette lighter and has one AC outlet

Solar Power Function #2 — Generating AC Power to run the TV

When an RV comes from the dealership, it usually has a shore power cable so you can plug the rig into electrical hookups or into a gas generator.  The shore power cable takes the AC power from the source (“hookups” or generator) and passes it straight through to your AC outlets. 

In other words, when the rig is plugged in like this, all the AC outlets, including “built-ins” like the microwave, become “live,” and you can run your AC appliances like the TV, computer, toothbrush charger, electric razor, hair dryer, vacuum, etc.

If you want to have AC power without plugging into shore power, you have to have an Inverter.  An Inverter converts the DC power that is stored in the batteries into AC power so you can run your AC appliances like the TV and computer. 

However, the Inverter is not technically part of the RV solar power installation.  That is, it doesn’t connect to the solar panels in any way.  You can use an inverter and not have any solar panels installed.  However, unless you plug into shore power, your batteries will get run down by watching all that TV!  That is why Inverters are lumped into the overall notion of RV solar power installations.  They are a vital component if you want to dry camp.

You can buy small, portable inverters for under $25 that will run your laptop from a cigarette lighter.  These work on the cigarette lighters inside an RV just the same as they work on the cigarette lighter in a car.  No difference.  If you are puzzled by all this, get a little power inverter and try it out.  I was totally enlightened the first time I turned on a small inverter in a car and saw the “charging” light on my laptop light up.

300 watt portable inverter

A 300 watt portable inverter ($20) with cigarette lighter plug and 2 AC outlets

A small 300 watt portable Inverters can run small 19″ LED TV too.  Anywhere from 300-500 watts is fine for pretty much everything in an RV except the microwave, hair dryer, vacuum and air conditioner.  You need an inverter of 1000 watts or more to run a small microwave, hair dryer or vacuum.  You can’t run an air conditioning unit from an inverter unless you have a boatload of batteries, something that few RVs can support because of the weight. To run our air conditioning, we use a Yamaha 2400i generator.

A 2000 watt inverter is fine for most things you might use.  You just can’t run the big appliances (microwave, vacuum and hair dryer) simultaneously.  If you are content using these appliances one at a time, don’t bother with an inverter larger than 2000 watts.  We power everything on the boat except the microwave with a 600 watt inverter.  We power everything in the fifth wheel, including the microwave, with a 2000 watt inverter.

Some higher end motorhomes come with an Inverter/Charger (see above), so they don’t need to have an Inverter installed – they already have one.  Turn on the Inverter/Charger, and shazam – all the AC outlets in the rig are “live.”

Atwood converter

A converter – this was factory installed on our fifth wheel

Most trailers do not come with an Inverter/Charger.  They come with a Converter instead.  So if you have a trailer, you will need to get an Inverter to watch TV.

This terminology is unfortunate, as “Inverter” and “Converter” sound so much the same.  However, they are almost the opposite of each other.

  • A Converter charges the batteries, i.e., it takes AC power from an external source — hookups or generator — and puts that energy into the DC batteries to charge them up.

  • An Inverter takes the DC power from the batteries and creates AC power so you can watch TV.



Wait, what was all that, again??

So, to recap:  when you install Solar Power in your RV, you are tackling two problems:  ( 1 ) Charging the batteries, and ( 2 ) Generating AC power from your DC batteries so you can watch TV, surf the internet, and charge your camera batteries.

You need three types of components or “parts” to do all this:

  •  An Inverter to create AC power out of the DC power that is stored in your batteries so you can use the TV and computer.  You can use little portable ones that plug into cigarette lighter outlets and/or you can install a big one.

If your rig came with an Inverter/Charger, you are halfway there and need only to add the components for charging the batteries (Solar Panels and Charge Controller).

Next Up: What you need for a small RV solar installation that’s good enough for summer weekends, vacations, and simple living on an extended tour.

Solar Tutorial Part II – A “Starter” Installation –>






Most of the components for an RV or marine solar power installation can be purchased at Amazon.

Shown here is a complete "weekender/vacationer" kit (far left), a small charge controller (middle) and a small inverter (right). More comprehensive listings of each component type can be found at the following links:

Purchases at any of our Amazon links help keep us going. But don't buy anything yet. Finish the tutorial first!


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How much inverter is enough?

Living totally off the grid on battery power in an RV or sailboat requires a good sized inverter to power the AC appliances like TVs, laptops, microwave, camera and cell phone chargers, hair dryers and vacuum cleaner.

But what is “good sized?”  How much is too much — or not enough?  What happens if you go over the limit? A recent mishap when we first returned to living in our trailer a few months ago sent us back to the basics and reminded us about limits, living skinny and living large while boondocking and living on a small inverter.

Exeltech XP1100 Power Inverter in the basement

Our Exeltech XP 1100 watt pure sine wave inverter lives in the
fifth wheel basement.

Figuring out the math behind the theory — the amps, volts, watts and conversions between them — and doing that for each appliance while guessing how much time each one will be used every day is downright daunting.

What’s worse — for people like I once was who are dealing with this stuff for the first time when they contemplate full-timing — just the terms “inverter,” “converter,” and “inverter/charger” leave us scratching our heads in bewilderment.  Techie phrases like “modified sine wave” and “pure sine wave” made my head spin when we first started out.

If that is the case for you too, have a look at our multi-part Solar Power Tutorial series where those terms (and many more) are explained in plain words.

As for inverter capacity, it is given in watts, and after living on several different sized inverters and inverter/chargers for almost seven years in two trailers and a sailboat, we have gotten a pretty good feel for what our moveable household of two people requires.  But that doesn’t mean we are immune to slipping up!

When we bought our full-time fifth wheel trailer in 2008, like most trailers, it did not have a factory installed inverter.  It had a 55 watt converter, and that was it.  (Most motorhomes have a factory installed inverter/charger that is wired to the AC outlets instead of a converter.)  So, we installed a pure sine wave Exeltech XP 1100 watt inverter

This is a top quality inverter that is built to such high standards that it can run very sensitive medical equipment off the grid. Exeltech inverters are used on the International Space Station to provide AC power to both the American and Russian sides of the station!

Sinergex Pure Sine Wave 600 watt inverter

This 600 watt pure sine wave inverter powered almost all
of our activities on the boat.

We chose that size because there was a huge increase in pure sine wave inverter prices once you got over about 1100 watts, and we had no single appliance on board that required more than that.  (In 2014 prices, the XP1100 inverter is ~$600 while the XP2000 inverter is ~$1,300).

The trailer’s microwave is 900 watts, and everything else we use (except the air conditioning which requires a generator anyways) is much less than that.  As long as we used only one big appliance at a time, all would be well.

The only real conflict that ever came up was when we used the microwave.  We had to be sure the TV was off and the laptops were running on battery power for the few minutes we used the microwave.  No big deal.

The sailboat we bought and moved aboard a few years after the trailer came with two factory installed inverters: a 2500 watt Xantrex Freedom 25 modified sine wave inverter/charger and Sinergex 600 watt pure sine wave inverter. The big inverter/charger was wired to all the AC outlets on the boat.  However, the little 600 watt pure sine wave inverter had been installed exclusively for the entertainment system: the two AC outlets on the inverter had two ordinary extension cords that went directly to the TV and the Bose 3-2-1 surround sound system.  This little inverter was independent of the boat’s AC wiring system.

The big modified sine wave Freedom 25 2500 watt inverter powered the microwave and vacuum.

The big modified sine wave Freedom 25 2500 watt inverter
powered the microwave and vacuum.

Because we had used a pure sine wave inverter in our trailer for a few years (and liked the idea of feeding our expensive computers a good quality signal), and because we assumed the big Xantrex inverter/charger would use a fair bit of power just to run in a “no load” state, we decided to rearrange the extension cords on the small pure sine wave inverter and use it as our primary inverter instead, running our laptops and charging up all our small appliances on it.

So, effectively, the only time we ever turned on the Xantrex inverter/charger was to use the boat’s 500 watt microwave that the factory had wired into the AC system, and to use our little dirt devil vacuum cleaner.  Everything else — 22″ LED TV, 13″ MacBook laptops, cameras, portable GPS/VHF radio, GMRS walkie/talkie radios, toothbrush, etc. — got plugged into a power strip coming from the 600 watt pure sine wave inverter’s AC connector.

Mark inspects inverter

Mark inspects the Exeltech inverter

This worked really well for us for the 3.5 years we lived off the grid on the boat.

However, when we moved back into our trailer, we were still living in the mindset we’d had on the boat, which made us careless with the microwave.  Whereas, on the boat, the 500 watt microwave was on a very big standalone inverter and we could use it without thinking, in the trailer, our 900 watt microwave shares the 1100 watt pure sine wave inverter with everything else on board.

One day, shortly after we moved back into the trailer, Mark popped some potatoes into the microwave for a few minutes.  We were deep in conversation as he puttered around the kitchen and I messed around with photos on my laptop.

I thought it was odd when I noticed the charging light on my laptop go out, and he thought it was odd when he went to hit the button on the microwave for the next round of potato-cooking to find that none of the buttons on the microwave worked.

What the heck?

Exeltech Exeltech XP 1100 inverter opened up

Well, at least nothing is visibly smoking!

We checked the usual things, and then went outside and around to the basement to see what the inverter was up to.  Eventually, we realized that the inverter had just died.

Yikes!!  This little black box is our life blood!  And it would be a pricey devil to replace.

After a rather solemn dinner with almost-cooked potatos, Mark removed the inverter from the basement and opened it up to have a look inside.

Ouch.  All four slow-blow fuses had blown.  But thank heavens the rest of it was fully intact and there were no charred marks or burnt looking things anywhere.

The trailer repair gods were definitely smiling on us.  We called Exeltech the next day to find out the fuse sizes (there were no sizes printed or etched on the blown fuses), and they were kind enough to put a few sets of fuses in the mail for us (free of charge!) to replace the four dead ones and to give us some spares in case of future mess-ups!

08 Exeltech XP1100 inverter slow blow fuses 451

Wait, what’s up with the four “slow blow” fuses?

However, we had a five day wait until the replacement fuses arrived.  It turns out that the size of these things is unique (35 amp slow blow). A sweep of the local auto parts stores turned up a few 30 amp slow blow fuses, which Exeltech said would work in a pinch, but Mark didn’t want to do the repair twice.

We liked our boondocking spot and didn’t feel like moving just to get electrical hookups, so, for the next five days we lived on a 350 watt modified sine wave inverter.

Sound crazy?  Well, it CAN be done!  We didn’t have to sacrifice too much.  We just had to pay attention.

We aren’t big TV watchers unless the Olympics or Tour de France is on, but we use our two laptops for hours every day.

In the good old days of 2007, this little inverter of ours could power our white 13″ MacBook without a hitch, no matter what application we ran or how discharged the laptop was.

Slow blow 35 amp slow blog fuses

All four “slow blow” 35 amp fuses are blown

However, we soon discovered that today’s 13″ MacBook Pro’s (2011 and 2012 vintage, non-retina display) — and today’s software (2014 vintage) — all use a lot more power.  Plus, we now have two laptops instead of one, which is more than the 350 watt inverter can handle.  So, we had to devise a sharing scheme.

There are a few tricks to this.

The power required to charge a laptop varies depending on the laptop’s state of charge and the way in which it is being used:

  • A laptop that has discharged batteries (nearly dead) requires more power to get charged up than one that’s 90% charged already.
  • A laptop in use, especially if it is running disk-access intensive programs (like photo manipulation software), requires more power to charge than one running something tiny like a plain text editor (think Mac TextEdit or Windows Notepad).
  • A sleeping laptop requires less power to charge than one that is in use
  • A laptop that is completely shut down requires the least power of all to charge

I don’t have any firm numbers, but my hunch numbers are that it takes about 5-10 times more power to charge a laptop that is nearly discharged and is humming away on a bunch of really big photo manipulation programs (or moving lots of files around on disk) than it does to charge a laptop that is near full charge already, is shut down and is simply plugged into AC power.

With all these things in mind — and since our laptop use was our biggest power use in the trailer (we didn’t even try running our 26″ TV with surround sound on the 350 watt inverter) — this was our daily strategy:

350 Watt Inverver

This 7-year-old 350 watt modified sine wave inverter powered our lives for five days.

First thing in the morning, we would run the laptops from their own internal batteries until they were about 50% discharged (about an hour or two). If we weren’t done on the computers at that point, one of us would connect to the little inverter while the other continued on battery power.

After an hour or so, we would usually want to get outdoors. We would turn both laptops off and connect the most discharged on to the inverter to get charged up.

We’d return home later and either begin charging the other laptop up, or, if we both wanted to get back on our computers, we would alternate use of the inverter and go through the cycle again.

As for the Exeltech XP1100 inverter repair, as soon as we got the replacement fuses, Mark popped them into the inverter, installed it back in its home in the basement, and life was good and AC power was abundant in our home once again.

Boondocking in North Phoenix Arizona 521

We were in a good spot. Why leave if we could make things work
for a while with a small inverter?

What did we learn from all this?

We can live simply when we need to!

Also, I’m really glad I asked the NuWa factory to install a cigarette lighter style DC outlet in the living room part of our trailer behind the TV (it came with one in the bedroom already).  This makes it easy to use a small portable inverter in a pinch.  In all honesty, I had questioned my sanity in asking the factory for this upgrade until this episode!

Then — on our next trailer (not that we’re getting a new one, but it’s always nice to think about that dreamy “next one”) — we will get a bigger inverter.  There is nothing wrong with 1100 watts, as long as we think for a moment before flipping the switch on the microwave.  However, in the next installation, we will be much more willing to spend double to get Exeltech’s 2000 watt pure sine wave inverter instead of their 1100 watt version.  A bigger inverter will also allow us to use our Vita-Mix (1600 watts) which has been waiting in storage until we finish this crazy off-the-grid traveling lifestyle (which isn’t happening any time soon!).

Lastly… we learned that the Exeltech XP1100 inverter is well protected from absent-minded users with four wonderfully precious slow blow fuses. Very fortunately for me, it was an easy fix for Mark to do. But it seems that it is a fix that anyone who dares open the inverter case could accomplish. They were inline buss fuses and they didn’t even require a fuse puller — just a screwdriver to lift them out.

Note: We installed an Exeltech XP 2000 inverter in April, 2015, and what an incredibly worthwhile upgrade that has been.

Learn more at our page: RV Electrical Power Overhual: New Batteries, Inverter and Converter

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Kyocera Solar Features Our Sailboat Groovy on their Website!!

Groovy Boat Solar Panel Installation

Groovy’s solar panel installation

Kyocera, the solar panel manufacturer, took notice of our sailboat Groovys solar power setup and has featured our story on the Kyocera Solar website.  We were very surprised and pleased when they contacted us (out of the blue) to say they wanted to feature us.

We’ve been using Kyocera solar panels since May, 2007, when we installed a single 130 watt solar panel on our first full-time RV, a 27′ Fleetwood Lynx travel trailer.  We have been living on solar power full-time in our moveable homes since then.

That first solar installation, like our first trailer, was a little small.  After a year of skinny solar living, we upgraded to 490 watts of solar power on a 36′ Hitchhiker fifth wheel trailer (which included some Mitsubishi panels because the store was out of Kyoceras in the size we wanted!), and we posted a page describing the two RV solar installations.  A few years later, with even more solar experience under our belts, we installed solar power on our sailboat Groovy.  And of course, we keep learning.  Our NEXT solar panel installation will be even snazzier!!

The gist of the story is the value of anticipating your needs before installing a system.  In general, from what we’ve learned over the years, more and bigger is always the best way to go!!

To learn more about solar power on RVs and boats, see our article, RV (and Marine) Solar Power Made Simple as well as our Solar Tutorial Series:

There are loads more solar power and battery charging articles on this site here:


Solar Power for RVs and Boats – Components, Design and Installation Tips

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