Pausing Windows When No Applications Are Open
You can conserve your Mac's CPU resources by setting Windows to pause automatically when no Windows applications are open. That way, less CPU resources are used by Windows services which allows you to save the battery and help the environment.
To set Windows to pause when no applications are open:
Do one of the following:
Click the Parallels Desktop icon in the menu bar and choose Configure.
If the Parallels Desktop menu bar is visible at the top of the screen, choose Actions > Configure.
Click Options and select Startup and Shutdown.
Select Pause Windows after and specify a period of inactivity after which Windows will be automatically paused.