You don't need to define a meter object to categorize energy use of fans. Fan objects have a End-Use Subcategory input field that tells EnergyPlus what meter subcategory to assign fan energy use to. The annual energy use of all subcategories (this can also be applied to lights, interior equipment, etc.) are summarized in the End Uses by Subcategory table of the Annual Building Utility Performance Summary report. You can read this post and this post for more information.
If you want to see the hourly energy use of these fan subcategories, then you would use an Output:Meter object and reference the subcategory that you defined in the fan object(s). To see a full list of all potential meter options in your model, you should review the MDD output file created after an EnergyPlus simulation. You could run a one-day simulation to generate this file first, add the relevant output meters to your input file, save the input file, then run an annual simulation to generate the meter data.
UPDATE
To answer your first comment's question, the end-use subcategory is a custom input field where the user can enter any category name they want. What they enter will appear in both annual summary reports as well as potential hourly meters.
To answer your second comment's question, NO -- any object with an input field for end-use subcategory (lights, equipment, fans, etc.) will only accept one input string. For example, if you wanted to make a subcategory for exhaust fans in kitchens, you should enter
Kitchen Exhaust Fans, !- End-Use Subcategory
This is because EnergyPlus only has one input field for meter subcategories, not multiple input fields like below.
Kitchen Fans, !- End-Use Subcategory 1
Exhaust Fans, !- End-Use Subcategory 2
To do something like this, you would need to alter the EnergyPlus source code and build your own version of the executable. So, if you want to apply 2-3 subcategories then come up with a naming convention for end-use subcategory input fields that reflect that.
