The title of the this post is a little misleading as clearly life on a boat is “off grid” but the system we have on-board is the same as if you wanted to work off-grid in a house. That is, 12V batteries charged by solar or wind. You can then run 12v appliances or 240V ones via an invertor.
Strangely, most appliances in a house are in fact running from 12 volts or less which is why laptops, lights, cameras and other appliances come with bulky adapters to convert them down from 240v to 12v or less. On our boat the only thing that needs 240v is actually our water-maker (desalination unit).