reply to ke4pym
Re: Keeping (upgrading) to (current) code - when does it apply? Nunya and Whizkid will be able to answer on the details, but something like adding a new circuit wouldn't require updating ALL the other circuits, otherwise it would be insane.
I'm renovating my basement, so that means 6-7 new circuits, all of which have to be up to the new code (And I'm going beyond the code too). However it would be insane for me to have to dig up all the old wiring from the upstairs floors to bring those up to code as well. It would be even more insane to require such an upgrade if you were adding ONE circuit for a dishwasher, or a receptacle in the utility room.
On the panel swap and solar panels, I'm not sure. Again, Whizkid and Nunya would be able to tell you.