I put the HPWC on the garage wall and pulled the cable from the subpanel at the back of the garage through the ceiling to the front of the garage.
I also pulled another cable on a separate breaker for a 14-50 plug to use as a back up.
Electrician says code here does not require conduit.
If you're going for 80A charging (100A circuit size), it's likely you'll use conduit, because even a #2 NM or SE (CU) cable isn't rated enough at the 60 degC column (see 334.80 and 338.10(B)(4)) - it's only good to 95A and 100A is required (219.10(A)(1)(a)). If you use wire-in-conduit, only #3 CU is required for 100A. Conduit is inexpensive and it's easy to pull the wires through when done correctly.
Only certain locales require conduit (Chicago and some parts of NY are the ones I know of).
See the FAQ located here (or link in my signature, below) for information on wiring.
[Technical stuff: If your wall is not insulated (which is unlikely, given it's likely an insulated garage or a fire break wall), you can use SER cable, but the moment it runs through an insulated wall, the 60 degC column is the limit. There was a loophole in the code prior to 2008 that would let you use SE cable at the 75 degC column, allowing you to use 3/3/3/5 CU SER, but that was closed in the 2008 code.]