Solar Panels; lots of cruisers are installing theses, and for good reason.
Save on fuel and wear and tear. If your boat does not have a generator, then you will be using your main engine. I’m not a fan of this choice, due to the high cost of overhauling your main engine. It cost much less to replace a gen set then the main engine. On our boat Jennifer K, we use the Honda 2000 portable unit. Weights only 50 lbs, runs for up to 6 hours on a gallon of gas.
Install 2 or 3 solar panels and your set for most of the time. Some customers ask about Wind gen units. We have installed several, and yes they work. But for our area (southern California) the wind is up and down, thus the output does the same, one minute you have 5 amps and just seconds later, you have zero.
I’ve seen boaters with as little as 250 watts to over 800 watts Installed. One of our customers has 400 watts, and he has power to burn.