What size conduit is needed to support 200A Mains supply?
(interested in the answer both for copper and aluminum)


The short answer is 2", that will hold the 250 Kcmil aluminum you would need
for a commercial 200a service. That's why it is the standard.
If this is a service mast you may need 2 1/2 for strength.
The absolute smallest would be 2/0 copper in a 1 1/4 or 4/0 aluminum in a 1
1/2. It is sure a lot easier to get the wire in a 2" for a few pennies a foot
more.