What size wire for a 400' run to a 200 amp service

Be ready to spend a ton of money!

Why do you need to pull 200 amps of service 400 feet? Did you call your local utility for a price, yet?

While I'm not an expert on the NEC code, I do know that utility owns the feeder side from either the pole or lateral connection point to the service entrance conductors. It is not covered by the NEC code.

Now if you purchase a transformer and connect or have a string of poles installed to the house or barn then code will carry the specs you need.

Speaking of service conductors, are you going to make your run from a pole transformer or a lateral transformer (underground) connection. The reason I ask is because underground cable can be run two ways, inside conduit and direct bury. The costs for this type of cable is higher than overhead cable. Not to mention the costs to trench 400 feet. On normal runs, you only have to go down 18 to put conduit in and 26 inches for direct bury cable. Then you have to back fill with 2 inches of sand before you lay the cable down.

Are you really sure you want to do this?

Please talk to your utility company.