The solar panels that we installed last May have been wonderful. We installed two 195 watt solar panels on swivel mounts near the stern. Having cruised full time since we'd like to share a few thoughts.
The pivoting mounts that mounted our panels on have been a success for entirely different reasons than we expected. We thought that we would track the sun with them. We've done very little of this. For the most part there is lots of power on board, and when there isn't we're usually spinning at anchor and would have to adjust them constantly. However, the pivoting mounts allowed us to put the panels far aft away from shade while giving us a means to easily stow the panels for safety when approaching docks.
We spent the winter in northern Mexico, mostly about latitude 25 North. From mid-December until early February the panels did not keep up with our power consumption. We rationed our power use, motored a few hours that we could have sailed, ran the engine once at anchor for power, and even plugged in to shore power overnight once. During this period we averaged perhaps 50 amp-hours/day from the solar panels.
Once the spring started to arrive the panels output started to increase significantly. By early March the battery bank was full every day before sunset with the panels having produced 100 amp hours or more. We were on the docks two weeks in Mazatlan and did not turn on the shore power charger for the batteries. We still have to ration the inverter as our many toys can easily draw 15 amps DC. After melting a double-zero AWG cable in early March, we have decided not to run the drier, hot water kettle, or microwave off of the inverter. Drawing 200 amps for even ten minutes is not good for our wiring. Perhaps if we cleaned all of the terminals better we could handle it, but as is we're not doing it anymore.
Having rationed power and done the other things that we did over the winter, we appreciate the essentially unlimited power that the panels provide even more than we did before. They are silent and so far maintenance free. And we have guilt-free use of our electronic toys.
We had planned on getting a wind generator, and consider it again from time to time. However with average wind speeds below 10 knots, we wouldn't average more than 20 amp hours per day, which isn't worth C$1,400 to us. For that kind of money we could get a pair of 120 watt panels and average at least 40 more amp hours per day. On the other hand, wind power usually comes when solar power is low, which is why we still talk about it from time to time.
One final thought regards the amount of power to generate. We have 195 watt panels because they are the largest that would fit. They are too much power sometimes, but too little at others. Calculating your power consumption and choosing panels based on that sounds like a good idea, but I have come to the conclusion that it is pointless for the following reason: your freezer is going to be your largest power consumer, and its power consumption is going to increase dramatically as the air and sea temperatures climb. Ours went from 10 amp-hours/day in Canada to 100+ amp-hours/day on hot tropical days. So you can't calculate your total power consumption to any degree of accuracy. So I recommend getting a couple of the biggest panels that will comfortably fit on your boat, or if you have an arch covering it with smaller panels.