It's normal behavior for Win8. By default, that operating system's core never shuts down all the way! It's part of a new feature — fast startup.
When you issue a standard power-down command to Win8, it carries out a hybrid shutdown. Win8 first closes and terminates all user sessions in the expected way. Next, it copies what's still running in RAM (primarily, the live core of the operating system — the system kernel) onto the hard drive. It then turns off the system hardware
To bypass the hybrid shutdown/boot process, do a command-line shutdown (e.g., shutdown.exe /s /f /t 00). Or embed the command in a custom tile.
Use Acer's Shift-key trick — other vendors probably provide something similar to trigger a complete shutdown.
Disable fast startup via the Shutdown settings in Win8's Power Options menu. Open the Win8 Control Panel (category) and click Hardware and Sound/Power Options/(change what the power buttons do)System Settings. Scroll to the bottom of the dialog box and deselect Turn on fast startup.