As part of the electrical refit I did a brief calculation of the daily power demand on the boat. I used the template from sailboat-cruising.com , which I liked because it distinguishes between anchor and under way, day and night usage and is easy to follow. With the estimation I tried to stay at the realistic side, assuming all-day fridge usage, autopilot, lots of instrument and chartplotter usage all day under way and more entertainment when at anchor. Our battery bank is sized to 300Ah accordingly, 2.5x of the highest calculated daily draw, so we don't deplete the batteries below 50%. Now we need to match the demand with the generated power.