I am often asked about adding a solar panel to a boat. My first question is why? The only real reason to add solar to a boat is because you want to have mechanical refrigeration. If this is the reason, and it is a good one, then nothing less than 300 watts should be installed. Solar panels need to be installed to have a clear view of the sun without any shading. The only location that really fulfills this requirement is to have the panels behind the backstay on some kind of support. This can be integrated with a Bimini or another sort of arch for this purpose. 300 Watts will be sufficient to keep the fridge running while the boat is at anchor indefinitely. If you are cruising constantly then you will need to upgrade this to about 500 watts or plan to use your alternator to top off your batteries.

Charging

How many devices do you need to keep charged? I have 2 ipads, an apple watch, an iphone and a computer, and this is just me! Each of these devices needs a plan to get charged on a daily basis.    You can now purchase usb charging ports that fit in the same hole that was used for auxiliary power. i.e. cigarette lighter sockets. It might be still good to retain one of these as there are still a few accessories that require these. The USB charging ports however do need to be installed around your boat in good locations. I personally have places that I can plug in 14 different devices. I don’t use them all, all the time but it is very helpful to have them in a number of convenient locations for myself or my crew. It is important to be careful when purchasing these as there are a couple of factors to consider. Power output needs to be about 2.5 amps. Many of these ports are only rated at 1 amp and will not charge your phone. They will keep it maintained if it is fully charged… but barely. It is also important to source marine rated units as the non-marine ones are very prone to rusting and will only last a couple of years.   

If you want to charge a computer, then you need to have a pure sine wave inverter. (not cheap). The cheap ones could damage your computer because of the saw tooth pattern of AC that they create.   A better option for charging computers would be a DC to DC converter that would change 12V DC to 19V DC, which is what most computers use. This needs to be carefully designed to ensure that the current is sufficient. It will be much more efficient than going to a larger inverter and then plugging in the power supply of your laptop.