Boat solar panel installation: How to fit BIG solar panels on a SMALL boat

Looking for information on boat solar panel installation? This post and my associated video explain the method I used to fit two large solar panels to a small sailing boat. Before getting stuck in to the details, let’s consider the following question:

Why should I fit solar panels to my boat?

Having enough electrical power to meet your power requirements, without having to run your engine or a generator to top-up your batteries, is extremely liberating.

My wife and I were able to spend twenty-three consecutive nights at anchor on our honeymoon (you can read more about our trip on this page) thanks to the solar panels I installed before we set off. We had plenty of power during our trip and we never had to run the engine to top-up our batteries (Note: to reduce the demand on the batteries, we did turn off our refrigerator at night).

There is something profoundly satisfying in being self sufficient like this and it opens up all sorts of possibilities for long term cruising… The following picture sums up how I felt on our honeymoon… (note the solar panels and my homemade folding tender!)

Okay, I get why it’s good to have extra energy generation capacity on board, but why should I choose solar panels?

Solar power is, in my opinion, the best solution for additional power generation on board a boat. This is for the following reasons:

Solar power is silent. Let’s face it, you need extra electrical power when you are not attached to shore power. Hopefully, this mean’s you’ll be anchored somewhere really beautiful and peaceful. Yes, some modern wind generators are fairly quiet and there are even some gasoline-powered generators, such as the Honda Super Quiet Generator, which you can use without giving you and the rest of your crew a headache. Listening to the waves lapping gently against your hull is the sweetest symphony and is only truly appreciated on a blissfully quiet boat… Solar panels are completely silent – and you won’t get any quieter than that!
Solar panels are extremely reliable. Modern solar panels are often guaranteed for 25 years. In the harsh marine environment, failure with technical equipment is very common. Salt water spray, powerful UV rays, humidity and the constant motion of boats can mean that the lifespan of equipment on board might be a tenth of what it would be for the same item used on shore. Solar panels are hermetically sealed and have no moving parts. They are pretty unique in being something you can add to a boat without adding to your maintenance workload.
Solar panels don’t need spares or consumables. Fitting extra gear onto a boat is often a challenge, especially on smaller boats where space is always at a premium. You might easily find room for a small generator but, don’t forget: you’ll also need to find room in an external locker for the fuel, you’ll need room in your tender to be able to carry the fuel, and you will need room on board to store the necessary spares for servicing / repairing the engine… The only spare I have on board for our solar system is a small, cheap and lightweight PWM charge controller, which I can use to replace the MPPT charge controller I installed in the event that it should ever fail.

How many watts do I need?

This varies from boat to boat and also from crew to crew. A boat with a single 50 watt panel might have no problems with power generation. An identical boat with two 50 watt panels might not generate enough to keep up with the demands placed on the system by the actions of its crew.

If you want to be serious about answering this question then you can calculate your power usage and then use the results to calculate the output of the solar panes required to meet those demands.

If you want a simpler answer then my advice is to have a good look at your boat and work out the maximum amount of solar panel wattage that you can practically get on board. As already explained, I believe that fitting solar panels is THE best way to generate power on board a boat. While you are making the effort to fit solar panels to your boat, you might as well fit as much as you can – without ‘going overboard’ of course!

Where is the best place to fit solar panels on a boat?

In my mind, the three most important factors to consider are:

Maintaining the safety and practicality of the boat. It would be possible to cover the walkways of a sailing boat boat with solar panels. However, if someone risks slipping overboard every time they approach the bow, the state of charge of your batteries will be the least of your worries…
Maximising the output of your panels. The output from a solar panel will plummet as soon as it receives even a small amount of shading. The effect is remarkable and if you want to test this, place a baseball cap on a large solar panel and watch the output fall off a cliff. I originally considered fitting our panels under the boom, where they were out of the way and easy to fit. However, once I worked out how much shading the panels would receive from the boom and mainsail, that location just didn’t make sense any more. If you can manage to find a way to angle the panels so that they are perpendicular to the sun’s rays, then you will fully maximise the output of your solar panels. I found an easy and cheap way to do this and I cover this in more detail in my video further down this page.
Making use of existing structures. Everything you add to a boat has some kind of negative consequence. By taking a good look at what structure you already have on the boat, you may be able to find a solution which makes the most of something which is already on the boat. For example, on my boat the solar panel mounts have made use of, and gain strength from, the existing pushpit. By using existing structures you will avoid uneccesarily adding windage and will have less things to polish! If you already have a radar arch then you may be able to modify that in order to fit your solar panels.

I cover these topics, and many more, in my YouTube video ‘How to fit Big solar panels on a SMALL boat’, below:

The video can be summarised as follows:

Step 1. Decide where to fit your solar panels.

Step 2. Buy the largest solar panels you can based on your budget and the space available on board.

Step 3. Buy a solar charge controller. I recommend investing a little bit more (on my boat an extra £40) to get an MPPT (Maximum Power Point Tracking) charge controller. These charge controllers not only reduce the voltage being sent to the batteries, like with a standard PWM charge controller, but they also simultaneously increase the amperage of the charge going to your batteries. Long story short: they squeeze the maximum efficiency out of your panels. While you are going to the trouble and expense of fitting solar panels, in my mind it is a wise investment to get a charge controller which wil maximise the efficiency of your system.

Step 4. Fit your solar panels. The video details my method of fitting the solar panels which allows them to be repositioned to track the sun. (I wanted to be able to sqeeze as much as possible out of my system) You can make your own version and the only tools you need are: a drill; some decent drill bits [Cobalt drill bits are ideal but you can manage with standard HSS drill bits]; some small spanners; and a pipe-cutter. If you’ve never used a pipe-cutter before the video demonstrates how easy they are to use. They are a great addition to your boat’s tool kit! ***I forgot to mention this in the video, but I also used Locktite on all the grub screws, and any nuts used are Nylock nuts. Because of this I can be confident that nothing will work loose over the coming years.***
Step 5. Run the cables and make the electrical connections. To get the most from your panels, wire them in parallel, rather than in series. This has the effect of making the two panels function more independently and any shading occurring on one panel will have less of an effect on the other.

One of my YouTube viewers made the following suggestion:

This is a great suggestion from Alan – I’ve searched online and the bicycle saddle quick release clips appear to be too large for my stainless steel tubing / dyneema combination. I could manufacture spacers to take up the play but I also have some doubts about the corrosion resistance of these type of clamps. If anyone has any experience using them at sea please let us know how they hold up.

I think I’ll eventually be able to find some stainless steel thumbscrew jubilee clips… If you know where I can find these then please let me know!

You can buy the solar panes, charge controller and pipe cutter here:

Solar panels https://amzn.to/2vRNmtx

MPPT Charge Controller https://amzn.to/2w9Q3WV

Pipe cutter https://amzn.to/2wdDNof

How will you be mounting solar panels on your boat? If you have any comments or questions then please post them below.

I hope this post has been useful to you. If it was then please share it on social media to help me put food on our dinner table.

Cheers!
Chris 👍