I have a 200A panel in the house and I want to install another 200A panel in the barn. Do I need a breaker box next to the house panel and where do I connect it, the meter? I have 200 feet of 2 inch conduit buried 3 feet, going out to the barn. What size aluminum wire do I run to the barn panel?

Ever so sorry but it is just not that simple.

To begin with, your main service panelboard may not accommodate a 200 amp breaker. It depends on the size of the breaker allowed by the manufacturer of the panelboard.

Logically, you cannot drain 200 amps for the barn off a 300 amp service panelboard. However, if you upgrade your electrical service to 400 amp and use a meter that allows a bypass feed to your barn you should be fine.

Questions:

How far is your barn from your residence?

Have you had a load calculation done to determine how much amperage is necessary to service the connected loads at the barn?