Minimizing the Unity Editor window, while it’s NOT in play mode, causes it to still consume a lot of CPU power. It varies between 5% to 12% on my system.
If the Editor is minimized and basically nothing it going on there, when it’s just “in idle” mode, the editor should be, like any other Application, use nearly 0% CPU / GPU.
The reason why I minimize an application is to dedicate more power to applications that are not minimized.