I didn't double check PattenP's math on his recommendation to go with 350-400MCM, but I'd try to go with aluminum for that large of cable and that distance as the dollars saved could be substantial. I'm assuming he suggested larger cable due to voltage drop.
Here's a gotcha though, the Square D box I just looked up QO142M200 is a 200A 42 space box. it accepts a MAX of 300MCM cable. So if you go with larger wire, you'll have to splice down to a smaller size wire to terminate to the load center. You can't change the lugs because they are part of the main breaker. They make crimp on wire size reducers specifically for this purpose, but it's an added expense. You might have to do the same thing at the meter end too.
Just thought I'd point it out before you went to terminate your wire just to find out a big wire doesn't fit in a small hole....
Here's another tip, If you are over sizing your wire due to voltage drop, you don't necessarily need to oversize the neutral. The neutral only carries the unbalanced current.
Another tip, if you are over sizing your wiring (for any reason) you also may have to over size your ground, there's calculations for that. But since this is a service, it's only 3 wire in the first place, so no ground wire between the meter and load center.
Brian
