Solar panels are no more of an afterthought for manufacturers than anything else.
On strictly financial grounds solar panels provide one thing and one thing only. They provide a means to power the boat when left moored and unattended.
Let me clarify:
One assumes you have a motor
. If so then it is cheaper to charge batteries via the motor
than via solar when one considers the capital cost of solar.
If you already have a generator for watermaker
machine, whatever, then it is cheaper to charge batteries via generator and inverter/ charger
when one considers the capital cost of solar.
Clearly, therefore, when on the boat you can either run motors or generator. Yes this uses fuel
but not much.
The problem arises when you are not on the boat and do not have shore power
. Automatic running of generators is risky imo so you are forced to rely on solar.
You can therefore size your solar so that it will power the boat for as many days as you leave it unoccupied, assuming that you have shed the power as much as possible.
Now this is ON A STRICTLY FINANCIAL BASIS. I realise many sailors want to be as green as possible so emotion enters the equation and they are happy to spend significant amounts of money
on equipping solar.
There is a third option to that mentioned here.
My personal view is that large arrays of solar panels are not only unsafe but unsightly and as such on my Helia I have equipped four 125W flexible panels.
In addition however I have an Anderson plug
attached to the batteries so that I can add on as much extra charging
capability as necessary by using floating arrays. These arrays are normally stored away when on shore power or sailing but are pulled out at anchor
and positioned to take full advantage of the position of the sun.
Accordingly I typically increase supply from 500W to 750W when at anchor. If I shut down the freezer
then the boat can be self sufficient. If I leave the freezer
on it would last a week of so.
is of course a different issue. If the boat is left the panels are placed so that they look like an attachment to the boat.
As far as recharging the batteries after a heavy night of lights, microwave, TV, computers
etc. etc. I have no problem in turning on the generator and if necessary the motors to charge the batteries.