October 6, 2014

Solar panels for boats: an easy installation guide.

Marine solar panel installation

In this article, I provide simple instructions for mounting solar panels on sailboats or powerboats.

When I first started sailing, I often found myself stranded at sea with a dead battery and no way to start my diesel engine. This is not fun or safe... I was using too much electricity and dragging my 12 volt battery down below 10 volts.

Finally, while sailing north to Alaska, I fixed this problem by installing this basic, solar panel boat system.

Here, I'm writing basic 'Do-It-Yourself' instructions to install solar panels for boats. All parts total cost me about $180, which is a great price to mount solar power on your boat. And it should be noted that I haven't skimped on quality, all the gear I used is well-respected, top brand stuff.

I installed the following set-up about 6 years ago, and everything is still working great (it's now 2016 as I update this article). Most importantly, not once in the past 6 years have I been left stranded at sea with a dead battery (knock on wood).

If you plan it right, you can have this finished in one weekend

Ok, a quick disclaimer

I am writing the following instructions for boat or RV people

This is a basic set up that provides a charge onto your DC battery bank.

This is perfect for keeping batteries topped off while you're disconnected from shore power. This means that while you're out fishing, sailing or anchored out for the evening - you can run your boat electronics (cell-phone charger, navigation lights, stereo, cabin lights, bilge pump, depth-finder, GPS ext...) and still have enough power on your batteries to turn over the engine and get you home.

If you want to use this system to power your home, then you'll also need an inverter to switch the DC electricity to AC.

Ok, here's simple DIY instructions for solar installation on a boat or RV.


How to install solar panels for boats


my 30 watt panel mounted on the railing along the stern of my boat

When I was planning what boat solar gear to buy, the consensus opinion was that a 30 watt panel was sufficient for my boat. My electrical needs are about 'light'. My electronic guru friend in Seattle pointed me to the 30-Watt Solar Panel featured in the photo above. Size-wise, it's compact (13x24 inches), which is nice, since it doesn't take up much space on the stern rail.

In regards to the power my 30 watt supplies...

If you average 5 hours of sunlight/day X 30 watts = 150 watt-hours per day.


You can also think about energy in terms of current (Amps.)

A 30W panel will give you about 1.8 Amps for 5 hrs a day. That is 9 Amp hours a day.

(sunlight hours will vary based on weather conditions)

I have used this panel in Seattle and San Diego, so the whole range of sun/cloud conditions and the 30 watt output has provided enough juice for me to use my electronics (stereo, GPS, depth-finder, cabin lights, cell phone charger, ext.) and keep my battery bank topped off.
(I've got two 12 Volt batteries, a deep cycle and a starter).

So, when I fire up the engine at the end of the day, my diesel turns over no problem.

solar panels for boats or RV
my compact 30 watt panel

Now, in regards to what panel to install... there's currently a bunch of high quality solar panels on the market. The industry is changing pretty fast, panel technology is constantly improving. Earlier this year, Jan 2016, as I was updating this page, I surveyed my boat and RV friends to see what panel they like best right now. Maybe 80 percent of them said they like Renogy panels. These panels are rugged, which is good for boats, they withstand stormy conditions. Plus you get a high quality panel (Amp. output) for the price.

If you are like me, a 'light' energy user, then go with the Renogy 30 Watts Solar Panel

Now, that said, many boaters would fall under 'moderate' energy users. These folks would want to run some kitchen appliances, maybe some fans, perhaps a water heater, ext...
In that case, go with a 100 watt panel. Their 100 Watt Solar Panel is the preference for mid-size boats with moderate amperage needs.

Campers/RV folks also seem to like this model.

Size-wise, the 100 watt panel is only about 45 inches by 20 inches. So, it should fit fairly well on your stern rail or RV rooftop.

And....if you want even more juice from the sun, then get 2 of these 100 watt panels and wire them together. Each panel yields 100 watts, so mount 2 of these for 200 watts total. Here's a photo of a RV rooftop with 4 of these 100 watt panels all wired together. Last month I helped a friend put a 100 watt on his 38 foot sailboat. We mounted it on the railing that sits on top of his canvas dodger (over the cockpit). He's very happy with the output. We used the compatible solar panel mounting bracket set to lock the panels onto his boat.

Here's the 100 watt panel on Amazon.

Okay, so once you've got your boat solar panel picked out, now you need to get yourself a 'solar controller'. 

This is necessary for controlling the charge coming off the panel. It is a small panel that is wired in place, in between the panel and your batteries. It enables the charge to be fed to the batteries at the right levels. It also prevents the batteries from leaking charge back out to the panel and prevents over-charging the battery. You need a controller, its not optional.

It's a simple device, but it's critical and you want a good quality controller. My guy at Fisheries Supply in Seattle told me to go with the Morningstar SunSaver-10, Charge Controller, 12V. I've had it in use for 6 years now and it's worked flawlessly for me. There's no moving parts here, its just diodes and fixed circuits. When the sun is shining, you get a green LED light on the top of the controller (see photo). This indicated that charge is going onto the batteries.
 I'm expecting this controller to last me another 10 years.

solar panel boat
the SunSaver-10 controller mounted in my cabin
Here's a link to that controller.

Step by step guide for installing a solar panel boat system

Ok, here's the quick summary on how to put this together.

 1.   Mount the panel on your stern rail (or where ever the panel gets sun and is out of the way).

 2.   Attach marine grade copper wires to the panel. These are DC wires for a 12 Volt system, so you need 2 sets of wires (black and red). Black (negative) and red (positive).

3.   Run the wires into the main cabin.

4.   Attach the wires to the controller.

5.   Attach a new set of the same marine grade wires from the controller to your battery.

6.   The red (positive) goes on the Positive terminal, the black (negative) goes on the Negative terminal.  (add a fuse on the positive wire, just upstream of battery terminal.)

7.   Crack a beer and relax while the sun tops off your batteries!

Now for some more detail:

Mounting the solar panel. 

DISCLAIMER: Every panel design will require a slightly different mount. The Renogy panels I mentioned above come with their own mounting brackets. This is probably preferred since their mounting brackets are only 15$.

But, apparently I like to do things the hard way. I went the 'Do-it-yourself' route and built my own mounting brackets to fit my stern rail. If you want to do what I did, here's how I did it.

My panel has an aluminum rail on the perimeter. Drill holes in this rail and attach 2 aluminum flats to serve as a center mounting rail. Attach these strips of aluminum with stainless bolts and nuts. To prevent galvanic corrosion (aluminum touching steel) use plastic washers. Then, attach these white plastic rail mounts to the new aluminum flats (or something similar). The beauty of these plastic rail mounts is you can adjust their tightness on your boat's stern rail. Therefore, you can push the panel around it's axis so that the panel is facing the sun throughout the day.

installing solar power for boats
the backside of my solar panel showing stern rail mounts

Okay, let's assume your panel is now mounted somewhere on the top of your boat or in the cockpit. Next thing is, connect the panel to the controller (the controller will be mounted inside the boat, usually by your other electronic panels).

Get yourself some Marine Grade copper wire. Get at least 30 feet of black and 30 feet of red. Check your specs. to determine wire gauge. If you're doing this install in a RV or cabin, save some money and do NOT buy the marine grade wires/terminals. You don't need it, just get the regular stuff.

install the solar panels for boats
marine grade copper wire for 12 volt DC electronics

Decide which terminals are best to use and attach wires to the bottom of the solar unit. There should be a contact box with a surrounding waterproof lid on the underside of the panel.

Then I use plastic zip ties to snug up the wires to the rail and down to the cockpit. Then find a small hole in your cockpit (or drill a small hole) and run the wires into the interior of your boat.

how to install solar panel boats
zip ties snugging up the wires to keep them from getting fouled

Okay - the rest is simple. Lead the wires to the mounted controller, then attach the incoming wires to the 'Solar + and -' screws. Then attach a new set of wires on the 'Battery + and -' screws. Run the battery wires to the battery terminals.

mounting solar panels on sailboat
one set of wires coming in from the panel, another set going out to the battery

And of course, use marine grade ring terminals to fit over the battery posts. As has been pointed out to me by some experts, you also want to include a fuse on the positive wire just before it hits the positive terminal on the battery. This makes for good protection of the circuit.

marine solar panel installation

Well, that should finish up your solar panel boat installation project.

Solar power for boats price breakdown

Morningstar SunSaver-10, Charge Controller, 12V
 about 60$

aluminum rails/plastic mounts/bolts/washers/zip-ties
(or do it professional with the Renogy mounting Z Brackets)
about 20$

marine grade wire (red and black) and terminals

Price-wise, you should be just around 180$ and you haven't skimped on quality products.

Alright, that's about all you need to get set up. 180$ is a small price to pay for mounting solar panels on a sailboat. Plus, its an eco-friendly way to keep your batteries topped off.

It sure beats getting towed back to port.

If... you don't want to deal with piecing this project together - then you also have the option of buying a 'solar kit' from Renogy. The kit arrives with everything you need to mount your panel. Here are the recommend kits for boats/RV with moderate energy needs. With this kit, you get their panel, their own controller unit, they include the necessary wires and terminals and they include their mounting brackets. This option is a bit more pricey, its about $300.00 for the 100 watt option, but it would make the project simpler. Less adventurous, but more simple...

Okay - Good luck with your marine solar panel installation!

Capt. Curran

Oh and by the way...

If you are unsure about your electrical diet (aka. how much energy you require), I also wrote up this page on how best to determine your solar panel wattage requirements. It's basically a guide to estimate how many watt/hours you'll be requiring on a typical day or week on the water. Once you've figured out how many watt/hours you require, you can then determine how large a panel you'll need.


curran said...

Heany -

Don't hesitate, the beauty of this system is that there are no moving parts, which means maintenance is minimal..

photons to electrons

FrankJ said...
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curran said...

Good question - visit your local machine shop
They should have barrels of aluminum flat panels
You want 12-16 inch long, need to measure panel

That's it

Then drill holes and strap in on the rail

Have fun!

Steven Keltsch said...
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Douglas Berry said...
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Kevin Curran said...

Thanks Douglass - all the best..

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Philip Magistro said...

Great information, thank you! Where did you purchase the white plastic rail mounts?

Kevin Curran said...

Hello Philip Magistro,

I bought them at a boating store in Seattle - called Fisheries Supply - they may ship.
But I would also check your local west marine - they are standard stern rail mounts - they fit lots of other stuff as well as solar panels.

Good luck !

Richard C. Lambert said...
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Home Solar Companies said...
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Lucas Logan said...
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Kevin Curran said...

Excellent, glad it was helpful. I'm about to post a couple new photos of the system. Everything is still working great.

Anonymous said...

Two questions
1. Is a 30w panel large enough to trick charge two 12v batteries?
2. How large an in-line on the positive lead to the battery?

Kevin Curran said...

Hello -

Yes, a 30watt panel is large enough to trickle charge 2 12 V batteries.
That is the set up I have on my boat - it works great - even in mixed sun/cloud conditions.

When you ask 'how large' an in-line on the pos. lead - I am assuming you're asking the guage. I can't give the exact guage that is suited for your set-up.
But, I know that the reasonable range is between 10-14 awg.
Hope that helps..


Anonymous said...

Thanks. Great info! I was actually trying to ask type and size of fuse on the positive lead to the battery. Fingers!
Bill Pierson

Joseph Addison said...
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Joseph Addison said...
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Lukas Wojtaszek said...

Thanks for a great post! I'll go with the Renogy 200 Watt kit. I know it's not as adventurous, but easier and faster. And time is money :)

Kevin Curran said...


I hear ya. Time is money - best of luck with that kit. I think you've made a wise decision....


Shawn Perez said...

Thanks a lot Kavin for your guidance on installing a solar panel on boat. As solar panels are the most effective and the best way of generating electricity these days so everybody wants to install a solar panel of their own. But installing a solar panel in the boat is little challenging. Thanks for sharing the step by step guidelines, it is definitely going to help the readers.

Mary said...

Great article. A few questions:

The article explains how to hook it up to one battery. But I have a system with two house banks of two bateries each, as well as a starter battery. How do I ensure that the trickle charge gets to all give batteries? Or do you just hook it up to the starter battery?

How does this system interact with my charger?

Kevin Curran said...


I have a similar battery bank - but the two are connected.

I connect the leads of the solar panel to my house batteries.

However, if they are not connected - then I would connect the leads of your solar panel to the starter battery.

emorillo2 said...

Mary, I would get a MorningStar SunSaver Duo controller which can charge 2 batteries (or banks thereof) and set the 2 house banks in parallel on the controller's Batt1 and the Starter Battery on Batt2. This controller has the option to charge 90/10 or 50/50, 90/10 is best for this setup because the starting battery doesn't need much, just enough to top-it-off.

Luis Evans said...
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Shapath said...