Sleep is set to Never when plugged in, which uses more power.

You can safely ignore the warning messages. If you set the screen and sleep time to “Never”, Windows 11 will always show the two warning messages below whenever you go into the power settings, to warn you about the power consumption. Thus, it doesn’t make sense to set a turn off screen time to have longer duration than sleep time. If your PC has already slept, it’s not possible for your screen to remain on.

You cannot set the sleep time to be shorter duration than turn off screen time. Note: The turn off screen time must be lower or equal to the sleep time.

You can select Never at the very bottom of the drop-down menu to tell Windows 11 to never turn off your screen or put your PC to sleep no matter how long your PC has been inactive.

Then, select a duration of time you prefer.

Next to the “ turn off my screen after” or “ put my device to sleep after” option, click on the timer drop-down menu.

Click on Screen and sleep to expand it.

Monitor keeps going to sleep