I use Avast on my computer that runs in a controlled environment. I use my computer for resource-intensive tasks, and when I am sure there is no threat, I disable all of Avast’s shields to prevent it from running.
However, even when I have disabled all the shields, all of its processes and services still run, and they use CPU and RAM. Here is a screenshot of the active processes:
Avast is designed to be a resident on access antivirus, although you can disable the shields temporarily, the background services would be running so that the shields and avast can start immediately.
The Avast Antivirus entries are for the avast user interface which has to be there to enable you to restart the shields, etc. Even though the Shields may be disabled as far as I’m aware the Virus definitions would still be updated.
I don’t see why you are getting this level of CPU activity as my laptop is hardly a high end CPU with Avast Shields enabled and running. Whilst composing this reply the Avast Processes/Services CPU activity is virtually 0% all of the time. Opening the Task Manager at that point and referring back to it is generating minimal activity.