As you correctly stated, if you are using eppy to generate the csv files you have to do.

idf.run(readvars=True)

Unfortunately idf.run(readvars=True) fails on some of the earlier versions of Energyplus. Test have shown that it will work on EnergyPlus-8-9-0

• This bug has been documented in two issues
  • https://github.com/NREL/EnergyPlus/issues/5058
  • https://github.com/NREL/EnergyPlus/issues/5898

Briefly:

• to generate the csv files Energyplus has to run ReadVarsESO after the simulations are complete.
• older versions of EnergyPlus have the ReadVarsESO located in an unexpected place.
• So it cannot run ReadVarsESO and will not generate the csv files
• ReadVarsESO is located in the right place in EnergyPlus-8-9-0 and the csv files will be generated here.
• Many of the earlier versions of Energyplus will also run ReadVarsESO successfully and will generate the csv files. But this varies on different platforms. If you are able to test and give me a list, I'll add it to the eppy documentation.