What is the collective noun for panel?

There isn't a widely accepted, single collective noun for "panel."

However, depending on the context, you can use:

For a group of people:

* Panel (This is the most common and straightforward option)

* Group

* Board

* Committee

* Jury (if it's a judging panel)

* Team

For a group of objects:

* Set

* Collection

* Series

* Array

* Assortment

The best choice depends on the specific type of panel and the desired level of formality.