Automatic shutdown hindered by sleep mode
You can use a third party tool like Power Manager to automate reliable shut downs.



By default, events will wake a sleeping Mac before being performed. Typically your Mac will be woken 15 – 30 seconds before the scheduled shut down begins. Ultimately, the wake up is performed by OS X's IOPMQueue which you can see and edit through the pmset tool.

I am the engineer behind Power Manager, so do ask if you need more details.