I am planning on building a large shed in the backyard, and am planning
on running electrical to it. I am getting a couple of books in on wiring
a house (including one called “Wiring a House”…) but would also be
interested in feedback from experienced electricians.

I have a few questions.

First, how is the easiest way to figure out what I have coming into the
house. My panel says 120/240AC 200 Amp, and I really have to believe
that is what is coming on, but I would like to confirm i have 200A. Does
it say on the meter? My bill? Or do I need to call the electric company?

Second, is there an easy, straightforward method of calculating current
“usage”, or load on the main panel? I am guessing the books will go into
this, but I wouldn’t mind getting some other input on this. I am
assuming I will have enough to add a 120V/15A dedicated for an electric
wall heater, and then one 15A circuit for the shed, since I recently
removed an electric stove in the house (replaced with gas), but I want
to confirm.

I was thinking it might be nice to have a sub-panel in the shed, with
the two circuits. Is there an advantage to this? I was thinking I could
feed the shed with 10g, and then have a 50A panel in the shed, instead
of running two separate wires for the circuits. My plan would be to hook
the feed wire to a GFCI breaker in the main, and then have two 15A
standard breakers in the sub. Is 10g enough for this load on an ~80ft
run (underground)? How would I wire it into the main panel? With one
single 50A breaker, or 2 25A, or some other way. Using 10g 2 w/g or 10g
3 w/g? I have not looked into how to wire a sub panel, so excuse my
ignorance.

Again, just looking for a base before I get my books.