Yes Ruatha, I agree on the practice of including solar panels. However, the flaw comes in to play once some significant battles take place. A coupla' solar panels per ship is not going to keep a fleet supplied when it's in enemy territory using lots of supplies putting down the waves of little ships being thrown at them.
Now the tactic of overwhelming the enemy becomes much more viable IMO. Weaponry uses a lot more supplies when its being fired (Well, of course you say...). Sure, if you leave the fleets alone, they'll be just fine, but who's going to let THAT happen??
