There are several output files available in EnergyPlus. As you can see in Appendix A, DataGlobals contains OutputFileStandard, OutputFileInits, and OutputFileDebug.
OutputFileDebug is initialized very early in the EnergyPlus execution and is available for any debugging output the developer might need.
OutputFileInits is intended for “one-time” outputs. If the value is calculated or entered and should be echoed to output, this file is the place for it. The structure is similar to the IDD/IDF structure in that there is a “definition” line followed by the data being reported. Since the data may be produced in several places during the simulation, the actual file looks a bit hodge-podge but can be easily imported into a spreadsheet program and grouped.
OutputFileStandard is the reporting variable output file from EnergyPlus. You can read more details from the Guide for Interface Developers document and in the Input Output Reference document. OutputFileMeters is a similar file to contain meter (only) output. Meter values also may appear in the OutputFileStandard file. Only values that change during the simulation should be output to these files. They are automaticallly included by the SetupOutputVariable calls.