To use the USB-CEC adapter or Intel NUC CEC adapter as a screensaver, powering off the TV when the PC becomes inactive and powering it back on when it becomes active again, first install libCEC 6.0.0: libcec-6.0.0.exe
Then click on the Windows icon, type "cec-tray" and start it.
Click on the Power Control tab and select a delay:
The TV will power off after the PC has been inactive for 2 minutes in this example and it will power back on when activity has been detected.
The progress bar indicates how long the PC has been inactive. The TV will power off once it reaches 100%, and it resets to 0% whenever activity is detected.