NOTE: This article refers to our previous boat. Adding significant solar was also the first major upgrade we did on our current boat — read about that here.
Our first major boat improvement was to significantly increase the solar power aboard Que Tal, going from 153 watts to 453. As a result, we virtually never ran the diesel (or a generator) just to charge the batteries — even with a decent-sized refrigerator in the tropics and a watermaker. We knew that the solar power would heat up the boat less, but an unexpected bonus was that the refrigerator ran less — the engine compartment was right next to the refrigerator, and not running it sure helped!
As our first big project, we struggled with numerous questions about whether it was worthwhile to do and how it would improve our cruising. I documented our analysis in “Dollars and Sense of Solar Panels,” published in Blue Water Sailing in February 2005. And yes, whether considered on a straight dollars and cents basis or in time saved (and spent on other, more fun, things), adding a bunch of solar panels was one of the best upgrades we made to Que Tal.
Admittedly, solar panels aren’t the right solution for every boat — you have to be cruising where it’s sunny. But the same framework for determining whether they’d be cost-effective for us, detailed here, can be used for other charging options, such as a wind generator or a gas or diesel generator.
The original article included a large sidebar on places to mount solar panels, with lots of photos. If the document does not show below (some browsers have problems), click here to view or download.
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Victor says
The one question that I have , that i did not see information about in the article , was , how many batteries are they running , and are they 6 volt or 12 volt ?
thank you
Carolyn Shearlock says
Thanks for asking, Victor —
We had 450 amp-hours at 12 volts. We actually had 4 Trojan golf cart 6 volt batteries, 225 amp hours each and hooked them together in parallel and series to form the 450 amp-hours at 12 volts. No change in the battery bank in the process of adding to the solar panels.
Carolyn
Al Felker says
1. When on shore power, do you turn off shore power battery charger?
2. When running engine, do you turn off solar charger?
I only ask because the solar charger will stop charging once it sees something else charging the batteries.
Carolyn Shearlock says
1. If the shore power was metered, we’d only use it when we needed to (sometimes we were doing power-intensive projects that used way more power than the solar had).
2. We never bothered to turn off the solar charger as we didn’t see any harm in leaving it on and then we didn’t have to remember to turn it back on when we shut down the engine.
Al Felker says
Do you turn off the solar charger when using shore, engine or genset?
The Boat Galley says
If they’re set up right, no need to. The regulator shuts the charge down then, and you might forget to turn them back on if you turn it off yourself.
Al Felker says
But if the other chargers see the solar regulator charging, they will not charge!
The Boat Galley says
Adjust the solar charger for 0.1 volt less and you won’t have the problem. Marine electrician set ours up that way and we never had a problem.
Al Felker says
Oh. Ok. Thank you. Must think.
Kelly says
What is the best brand of solar?
Carolyn Shearlock says
Solar is constantly evolving and the “best” brand constantly changes. A year and a half ago, we used SunPower Technology on our new boat and are very happy. You can read more about that installation here: https://theboatgalley.com/solar-upgrade/