You make some really good points. It can be difficult to consume in moderation when there's so much abundance. And when you add in the convenience factor (like for food) it becomes even more difficult.
As far as why to conserve when there's unlimited sun energy... I don't think it will get to this point. There are costs associated with producing the sun-catching equipment. There are resources that go into producing it, time to make it, labor to install it. So I don't think energy will be virtually free. Besides, the utility companies will still want their cut. Those in power (pun intended) like to stay in power and will do what they can to make that happen. Therefore, if someone comes along and says they can do it for free, the powers that be will work against them.
Still, it's important at a personal level to be disciplined in not over-consuming. It helps us to not get stuck in patterns of consumption and allows us to have excess that we can use to help others. And I think it gives us a little more peace of mind to not be worrying about what stuff we have to get next.
Thought-provoking stuff. Thanks.