The Revit out-of-the-box (OOTB) Electrical Equipment do not have the ability to host generic annotations (symbols). Now a typical workflow when creating Revit families is to start with one type of family and to change it to another.
What most people do not initially realize is that the default Revit parameters that are applicable to a certain type of family are automatically created when the family type is changed.
In the example in the video below, a metric generic wall-based family is changed into an Electrical Equipment, Panel family. Bar the electrical connectors, which one would have to place and assign the relevant values to, there is little else to do in terms of parameter creation. The great thing now is that the family can host a generic annotation family (symbol). Using the graphics overrides in the family allow one to indicate that model geometry is switched off in a course view, while the symbol is displayed, and vice versa.
If you need help creating ME families, please contact Micrographics so we may be of assistance to you.