By default Windows 8 updates automatically, and turns on the computer to do it. But you can easily change this behavior in Windows’ Action Center.
Windows 8 can automatically check for updates, even if the computer is turned off. By default this happens, every night at 3:00 am. But you can easily change the schedule and disable having your computer automatically powered on. Here’s how.
How to Customize the Windows 8 Update Schedule
From the Windows 8 Start Menu or search (Ctrl + W), type: automatic maintenance and click the link from the Settings results.
The Action Center for Automatic Maintenance will open up. In this screen, the update schedule can be set to a different time. There’s also a checkbox you can uncheck, so your system doesn’t power on to update.
Once set to the desired time, click OK to save changes and exit.