Windows 8 can automatically check for updates, even if the computer is turned off. By default this happens every night at 3:00am. But you can easily change the schedule and disable having your computer automatically powered on. Here’s how.
From the Windows 8 Start Menu or search (Ctrl + W) type: automatic maintenance and then 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.