Quote "
being a man in the know,
would you know if 6x100 watt solar panels be enough to keep the batteries topped up without having to run the engine for a few hrs every day?
also how much roughly does the average engine cost to run per hr?
cheers"
600w of solar, (through a mppt controller) will provide a useful amount of power during the summer, and about 1/10th of it in winter
(it all depends, of course, on how much power you need - which is why folks suggest you do a power audit first - - determine how much power you need, and then design a system to provide the power.)
A 1.5Ltr BMC engine uses between 0.75 and 1Ltr of diesel per hour on idle (just driving alternators). but you also need to factor in maintenance costs, and, if being thorough - replacement costs too.
When I calculated the overall generation costs incurred with our (bigger) Beta engine - It came out at about >£1.00 per Kwh.
(And solar is a great deal quieter too) - but like all systems on boats - it's most practical having more than one system for everything, (and to all intents and purposes, you will not ever heat water using pv panels)