I recently build a second separate garage. I have done the interior wiring and was going to upgrade the house service to 400 amps (from 200 amp) and run 200 amps to the garage. The main reason is that the power company did not want to run directly to garage due to 1. having to go around septic tank/drain field, patio and underground gutter drains in one direction and 2. having to go under or dig up my driveway in front of attached garage. My new garage is about 8' from attached garage and I anticipated running wiring through attached garage attic and underground to new garage. I am concerned about having a 400 amp panel installed and running the 200 amp wiring to new garage. Also a 200 amp breaker is over $400.00, I want to know if I should try to run two 100 amp cables to the new garage or is their a better method?

I see no cost benefit to running two 100 amp feeders and panels. Better off running the one 200 amp.

It is possible to run the two 100 amp.

The choice is up to you.