If you’re thinking about installing solar panels on your boat, or you’re just looking for benchmarking ideas, this is a great post to learn about solar panel installation cost and process.

Non-Technical Overview

When we bought Hobbes, there was an existing array of solar panels mounted above the dinghy davits. That contains 4 panels, 55W each, for a total of 220 watts. One of our first improvements to the boat was to upgrade the solar controller for these panels. The controller is wired in between the panels and the batteries, and it controls how much electricity goes into the batteries based on what the batteries are telling it (do they need juice? Are they fully charged?), so it’s performing an important job.

We  wanted to install a hard top is so that we could increase our solar power. 220W isn’t enough for us, we want to be off-grid without running the engines or generator just to keep the fridge on.

Kyle designed the hard top in conjunction with the large solar panels we’d purchased. We added 720 watts of solar, and we bought a separate controller for the new panels – we now have a grand total of 940 watts of solar power.

When we’re running the engines, they are charging our batteries, which means the controllers are telling the solar panels not to put very much electricity into the system. Since we’ve motored a lot, we haven’t gotten very good data for the panels until the past couple weeks when we’ve been at anchor. Now we’re using the panels to their full potential, and we can see how much they’re putting out and assess if it’s keeping up with our use. Very good news: we barely have to monitor our usage, even when we’re spending a lot of time on our laptops with the TV running in the background. We can’t tell what our daily usage is, but it looks like it’s been roughly on par with our solar output, probably around 3500 watt-hours per day (3.5 kWh). The average household uses 28.9 kWh per day, so you can see how much we’ve reduced our carbon footprint by moving aboard a boat.

Our total for solar panel installation cost was $1533, this includes the new solar panels and accessories. Since, at the time of writing, we’ve made 158 kWh of power since installation in January, our cost per kWh is under $10/kWh. The US average cost per kWh is $0.1247, so it would take us around 20 years of using these panels to be competitive with household rates for electricity. It’s not apples to apples, of course, because at anchor we don’t have the option of hooking into the electrical grid, plus we can be smug about not using fossil fuels like most households do. This is just a fun comparison. If we factor in the costs of installing the hard top, it would take us even longer to break even, but adding a hard top and solar also increased the value of the boat.

Okay, that’s a good overview, let’s get technical about what we own and why we own it!

Solar Panels

Kyle sourced high voltage panels from Craigslist, the seller used to install them on houses before he realized there was much better money to be made buying panels in bulk and reselling them to schmucks like us. We got a good deal on new panels, the downside is that they don’t have a warranty. We bought two 360 watt panels for a total of $378. Most boats opt for solar panels with smaller overall dimensions, but since we have the real estate to support these (our cockpit roof), this was a really good option for us. Our panels are made by JA Solar.

You can find solar panels on Amazon for $1-2 per watt, since we bought from Craigslist we managed to get our cost down to $0.53 per watt. Go ahead and cheap out on solar panels! Save your money and use it on a good solar controller.

Since we got our panels from Craigslist there’s not much technical detail to add here, but if you’re looking to do something similar, this is a great resource for learning about solar power installations.

Solar Controller + Display

It doesn’t really matter what kind of solar panels you’ve got, the important thing to get right is the solar controller. Buy the best controller you can afford – that’s how you maximize panel efficiency without losing those hard-earned watts to heat loss and output current limits.

We bought high-voltage solar panels (the kind you’d put on a house array), so we had to purchase an MPPT controller which also increases efficiency by 10-15% compared to other charging methods. The MPPT controller we bought can handle up to 150V, the panels we bought put out 48V nominally. A PWM controller would limit us to 12V, it’s typically used in smaller systems – there are no shortage of sites that debate PWM vs MPPT online, but here’s Kyle’s 10 second overview:

We bought a MorningStar controller for the 48V panels ($598). One of the benefits of this controller is that it is wired in to our boat network, which means when my laptop or phone is connected to the network, I can navigate to the IP address for the controller and I get a fancy real time readout of our charging status. This controller also comes with a big heat sink rather than a fan, which is nice because a fan could fail and let the system overheat. Here is the Morningstar calculator Kyle used to determine which controller we needed. We also purchased a digital display for the controller, since it does not come with any display ($112).

One thing I’d like to note here is that the 55W panels are still using the controller we bought initially, and the 360W panels use the MorningStar controller. The main reason to keep them separate is that in order to add the 55W panels (12V) to the MorningStar controller, Kyle would have had to rewire them to output 48V, just like the 360W panels. Another benefit of having them separate is redundancy – if one array or controller goes down, theoretically the other one should still be fine.

Kyle wired the 360W panels in parallel, which keeps the output at 48V (wiring in series would put it at 96V) and also minimizes the effect of the boom shading the panels – with one cell shaded, we lose 33-50% of the output of that panel. If the panels were in series we’d lose a large portion of the entire array’s output. While we’re talking about wiring, our big panels have 8GA wiring ($159), which is huge, but it helps minimize losses. With wiring like this, it never hurts to go bigger, but if the wire is sized too small there will be voltage losses due to resistance, and that will reduce the overall efficiency of the system. Our panels specify 12GA minimum, Kyle also uses this site to calculate wire size. We also purchased MC4 Branch Connectors and MC4 Solar Connectors for the exterior connections ($15), rather than building a box for connections.

Network Display

This is the best part of our solar installation. The Morningstar controller is wired into our boat network, so I can check any device (laptop, tablet, phone) and get real time solar data. The max potential output is 720 W, and we’ve come pretty close to that, which is impressive because our cockpit roof slopes downward on either side, so there’s never a scenario in which both panels are directly facing the sun.

The network display also has a log of the past 100 days. We’ve had pretty much all sun since we got to Florida (ahem, notable exception, ahem), but we’ve also been running the engine quite a bit as we travel down the ICW. When the batteries are fully charged, the controller reduces the solar panel output, so a lot of those days we were at either Absorption or Float, which means the solar output numbers are low for those days. That being said everything is always a contest, so far our best days have generated above 4 kWh!

Fuse

Kyle put in a fuse in between the solar controller and the batteries, which is an important safety feature – if something shorts the wires, the fuse blows rather than starting a fire in our battery compartment. We bought a fuse and fuse block ($39).

Monitor

Kyle installed a monitor ($185), which is connected to the batteries. It just displays one meaningful thing: our net amps going in or out of the battery bank. This is the sum of all the amps coming in from all the solar panels, minus all the draws from any electricity usage. Typically, sitting at anchor, we’re drawing amps to run the fridge, freezer, fans, and the inverter to power our laptops. On a sunny day, with everything running, we’re still putting up to 45 amps into the battery bank. For comparison, our alternators each put about 40 amps in.

I love our solar panels. With this kind of power generation, we hardly ever have to monitor our laptop or TV usage unless we get a few cloudy days in a row. At night the monitor displays a negative number, because we’re only drawing power and not putting any back in. In the photo below, the monitor is on the left, and the solar controller for the 55W panels is on the right.

Supposedly the monitor also shows how charged your batteries are, as a percentage, but this either isn’t working or isn’t set up correctly. If this was working, it would be a great indicator of when we should curb our electricity usage or when we’ve got plenty of juice.

Temperature Sensors

One last thing Kyle added to the solar controller is a temp sensor for the battery bank ($26), so the charge controller can even more accurately charge the batteries. With this installed, when I look at the real time data on the network, I can also see the temperature of the battery bank.

He also put a thermostat with a digital display ($8) above the solar controller heat sink that kicks on a fan to ventilate the locker when it’s warm.

Solar Panel Installation Cost Breakdown

• Two 360W panels: $378
• Solar controller: $598
• Solar controller digital display: $112
• Wire: $159
• Branch/solar connectors: $15
• Fuse/block: $39
• Monitor: $185
• Temp sensor: $26
• Thermostat: $8
• Misc hardware: $13
• TOTAL: $1533

So if you thought $1-2 per watt was a good deal on solar panels, you’ll be shocked to see that we’ve installed an entire solar energy system for $2.13 per watt!

Is Kyle a Genius?

I mean, yeah, he probably is. But he has more than just a passing interest in renewable energy, solar power specifically. We’re talking about a guy who wrote papers about solar energy when he was in college, if he was allowed to pick the topic. Not only is this system based on hour upon hours of research, but he genuinely enjoyed every minute of it. And it shows! He’s got a real passion for this topic – if you have any questions, ask them below and we’ll make sure you get answers!

However, this is the same guy that tried to take photos of us out in the dinghy the other day, but when I transferred them to my laptop all I found was 13 videos of varying length. So you’ve gotta take the good with the bad. (I’m pretty sure if I keep doing this, he’s going to start his own blog to tell you about all my foolish mistakes. I wonder if I could pre-empt this revenge by posting a few of my more innocuous stories…)

Seriously, he did an amazing job putting this together, and, in typical Kyle fashion, it goes above and beyond the minimum functionality so that we’ve got extra safety features and system monitors. We can stay on top of any abnormalities before they become expensive problems.

The only reason I’m writing this instead of Kyle is so the average reader can understand it, if Kyle authored this text it would read like a technical manual. This is why we make such a great team!