I have a 7 watt panel that I leave out in the cockpit when I'm off the boat or up on the dodger while at anchor. The panel is connected directly to the batteries, no need for a controller on a little guy like this. It keeps the batteries topped up while I'm not on the boat and does not need a permanent installation. The only thing I did was add a connector to plug it in beside the engine control panel (and a fuse of course). If I was going to spend a few days between running the engine while on board I'd get more solar panels before thinking about a wind or gas generator.