Above ground or under ground in pipe? Aluminum or Copper?
Run 250mcm AL if you plan on really loading the panel up with welders compressors etc... run 300mcm AL. If your rich run 3ott or 4ott copper
I'm thinking about under ground, but it may have to be run elevated between poles.
Thank you Woodbridge and Brighten.
If the application is residential,smaller wire sizes are allowed, per NEC Table 310.15 B6, which states 200 amp service or feeder can be either # 2/0 copper or 4/0 aluminum. However, if you are underground, larger is better as heat generated by the wire cannot be removed, Overhead wires have the advantage of cooling to the air that surrounds them.
if overhead also wire can not be lower then three feet over building, with roof pitch less then 24 on 12, or at least eight feet from flat roof. And service connections and wires cannot be reached from windows by at least three feet. 10 feet above highest walking level, 12 feet above residential property and 18 feet above streets, alleys or parking areas.
310.15 is for dwellings not shops that are detached from the home. Don't use that chart! Put your wire under ground if you have the choice and put it in conduit like 2-1/2in pvc sch40. Remember always check your local codes before taking any of our advice.