EnergyPlus File
Extensions[LINK]
This section will present a list (perhaps not complete) of
EnergyPlus file extensions and what they mean. This will help
you after the EP-Launch program finishes.
The following files are input to the EnergyPlus
program.
The input data dictionary (IDD) is an ascii (text)
file containing a list of all possible EnergyPlus objects and
a specification of the data each object requires. This file is
analogous to the DOE-2 keyword file. The Guide for
Interface Developers contains a full description of the
input data dictionary.
The input data file (IDF) is an ascii file
containing the data describing the building and HVAC system to
be simulated. Many example files are installed as part of the
EnergyPlus installation. Additionally, a spreadsheet file
“ExampleFiles.xls” contains columnar descriptions of each
file’s features.
The input macro file (IMF) is an ascii file
containing the data describing the building and HVAC system to
be simulated and will have some contents of “macro” commands.
The Auxiliary programs document describes use of the macro
commands and the program that processes them - EP-Macro. Many
example files are installed as part of the EnergyPlus
installation.
This is the EnergyPlus initialization file. It is an
optional ascii input file that allows the user to specify the
path for the directory containing Energy+.idd. This file,
using the actual directories of the install, will be created
during the install. Unless you change where the EnergyPlus.exe
file resides, you will not need to change this file.
The EnergyPlus weather file is an ascii file
containing the hourly or sub-hourly weather data needed by the
simulation program. The data format is described in detail in
the Auxiliary Programs Document. It is also described
succinctly in the Input Output Reference document.
More information (and more up-to-date) about output files
is shown in the Output
Details and Examples Document.
A text file containing the error messages issued by
EnergyPlus. This is the first output that should be
examined after a simulation.Error messages may be
issued by EnergyPlus during its input phase or during the
simulation. There are three levels of error severity:
fatal, severe, and warning as well
as simple “message” lines. A fatal error causes the
program to terminate immediately. The following table
illustrates the necessary actions.
Table 33. Error Message Levels - Required Actions
|
Error Level
|
Action
|
|
Information
|
Informative, usually a follow-on to one of the others. No
action required.
|
|
Warning
|
Take note. Fix as applicable.
|
|
Severe
|
Should Fix
|
|
Fatal
|
Program will abort
|
An example of an error message due to an input syntax error
is:
** Severe ** Did not find " DessignDay" in list of Objects
** Fatal ** Errors occurred on processing IDF file -
probable incorrect IDD file. View "audit.out" for details.
************* EnergyPlus Terminated--Error(s) Detected.
This is an text file which echoes the IDD and IDF files,
flagging syntax errors in either file. Note that both
err and audit will show most of the error
messages caused by input syntax errors; however only
err will show errors issued during the actual
simulation. The audit can be used when you need to
see the context of the error message to fully ascertain the
cause. The audit file also contains potentially extra
information that may be useful from the input scan.
The EnergyPlus Standard Output (ESO) is a text
file containing the time varying simulation output. The format
of the file is discussed in the Guide for Interface
Developers and the InputOutputReference. The
contents of the file are controlled by Output:Variable
commands in the IDF file. Although the ESO is a text file, it
is not easily interpretable by a human. Usually postprocessing
will be done on this file in order to put it in a format that
can be read by a spreadsheet; however a quick visual
inspection of the file does show whether the expected
variables are output at the desired time step.
The EnergyPlus Meter Output (MTR) is a text file
containing the time varying simulation output. The format of
the file is similar to the ESO file. As described in the
Getting Started document, meters are a powerful reporting tool
in EnergyPlus. Values are grouped onto logical meters and can
be viewed the same way that the ESO variables are used. The
contents of the file are controlled by Output:Meter
commands in the IDF file. Although the MTR is a text file, it
is not easily interpretable by a human. Usually postprocessing
will be done on this file in order to put it in a format that
can be read by a spreadsheet; however a quick visual
inspection of the file does show whether the expected
variables are output at the desired time step.
This file contains all the details (i.e., which report
variables are on a meter and, conversely, what meters contain)
about meters.
The EnergyPlus Invariant Output (EIO) is a text
file containing output that does not vary with time. For
instance, location information (latitude, longitude, time
zone, altitude) appears on this file.
The Report (variable) Data Dictionary (RDD) is a
text file listing those variables available for reporting (on
the ESO) for this particular simulation. Which variables are
available for output depends on the actual simulation problem
described in the IDF. The Report (meter) Data
Dictionary (MDD) is a text file listing those variables
available for reporting (on the MTR) for this particular
simulation. Which meters are available for output depends on
the actual simulation problem described in the IDF. A
simulation with no chiller would not permit the output of any
chiller report variables. The user may need to examine the RDD
or MDD to find out which report variables are available in a
particular simulation. The RDD and MDD are written only if the
following is included in the IDF file.
Output:VariableDictionary, Regular;
A variant produces the same files in a IDF “ready”
format.
Output:VariableDictionary, IDF;
This is a text file containing debug output for
use by EnergyPlus developers. Generally developers will add
debug print statements wherever in the code that that they
wish. There is a “standard” debug output that prints out
conditions at all the HVAC nodes. This output is triggered by
placing
Output:DebuggingData,1;
in the IDF file. If Output:DebuggingData,
0 is entered, you will get an empty eplusout.dbg file.
This is a file in AutoCad DXF format showing all the
surfaces defined in the IDF file. It provides a means of
viewing the building geometry. The DXF file from EnergyPlus
highlights different building elements (shading, walls,
subsurfaces) in differing colors. A number of programs can
read and display DXF files. Output of this file is triggered
by
Output:Reports, Surfaces, DXF;
in the IDF.
A text file containing the coordinates of the vertices of
the surfaces in the IDF.
Output of this file is triggered by
Output:Reports, Surfaces, Lines;
in the IDF.
Postprocessing
Program/Files[LINK]
A postprocessing program ReadVarsESO.exe is
available that will read an ESO or MTR file and produce a file
that can be read by Excel™. It can use an input file or not.
In batch mode it is run by the little batch file
RunReadESO.bat: Further information on this program
is provided in the Input
Output Reference under a section heading called “Using
ReadVarsESO”.
EnergyPlus File Extensions[LINK]
This section will present a list (perhaps not complete) of EnergyPlus file extensions and what they mean. This will help you after the EP-Launch program finishes.
Input Files[LINK]
The following files are input to the EnergyPlus program.
IDD[LINK]
The input data dictionary (IDD) is an ascii (text) file containing a list of all possible EnergyPlus objects and a specification of the data each object requires. This file is analogous to the DOE-2 keyword file. The Guide for Interface Developers contains a full description of the input data dictionary.
idf[LINK]
The input data file (IDF) is an ascii file containing the data describing the building and HVAC system to be simulated. Many example files are installed as part of the EnergyPlus installation. Additionally, a spreadsheet file “ExampleFiles.xls” contains columnar descriptions of each file’s features.
imf[LINK]
The input macro file (IMF) is an ascii file containing the data describing the building and HVAC system to be simulated and will have some contents of “macro” commands. The Auxiliary programs document describes use of the macro commands and the program that processes them - EP-Macro. Many example files are installed as part of the EnergyPlus installation.
ini[LINK]
This is the EnergyPlus initialization file. It is an optional ascii input file that allows the user to specify the path for the directory containing Energy+.idd. This file, using the actual directories of the install, will be created during the install. Unless you change where the EnergyPlus.exe file resides, you will not need to change this file.
epw[LINK]
The EnergyPlus weather file is an ascii file containing the hourly or sub-hourly weather data needed by the simulation program. The data format is described in detail in the Auxiliary Programs Document. It is also described succinctly in the Input Output Reference document.
Output Files[LINK]
More information (and more up-to-date) about output files is shown in the Output Details and Examples Document.
err[LINK]
A text file containing the error messages issued by EnergyPlus. This is the first output that should be examined after a simulation.Error messages may be issued by EnergyPlus during its input phase or during the simulation. There are three levels of error severity: fatal, severe, and warning as well as simple “message” lines. A fatal error causes the program to terminate immediately. The following table illustrates the necessary actions.
Table 33. Error Message Levels - Required ActionsAn example of an error message due to an input syntax error is:
audit[LINK]
This is an text file which echoes the IDD and IDF files, flagging syntax errors in either file. Note that both err and audit will show most of the error messages caused by input syntax errors; however only err will show errors issued during the actual simulation. The audit can be used when you need to see the context of the error message to fully ascertain the cause. The audit file also contains potentially extra information that may be useful from the input scan.
eso[LINK]
The EnergyPlus Standard Output (ESO) is a text file containing the time varying simulation output. The format of the file is discussed in the Guide for Interface Developers and the InputOutputReference. The contents of the file are controlled by Output:Variable commands in the IDF file. Although the ESO is a text file, it is not easily interpretable by a human. Usually postprocessing will be done on this file in order to put it in a format that can be read by a spreadsheet; however a quick visual inspection of the file does show whether the expected variables are output at the desired time step.
mtr[LINK]
The EnergyPlus Meter Output (MTR) is a text file containing the time varying simulation output. The format of the file is similar to the ESO file. As described in the Getting Started document, meters are a powerful reporting tool in EnergyPlus. Values are grouped onto logical meters and can be viewed the same way that the ESO variables are used. The contents of the file are controlled by Output:Meter commands in the IDF file. Although the MTR is a text file, it is not easily interpretable by a human. Usually postprocessing will be done on this file in order to put it in a format that can be read by a spreadsheet; however a quick visual inspection of the file does show whether the expected variables are output at the desired time step.
mtd[LINK]
This file contains all the details (i.e., which report variables are on a meter and, conversely, what meters contain) about meters.
eio[LINK]
The EnergyPlus Invariant Output (EIO) is a text file containing output that does not vary with time. For instance, location information (latitude, longitude, time zone, altitude) appears on this file.
rdd[LINK]
mdd[LINK]
The Report (variable) Data Dictionary (RDD) is a text file listing those variables available for reporting (on the ESO) for this particular simulation. Which variables are available for output depends on the actual simulation problem described in the IDF. The Report (meter) Data Dictionary (MDD) is a text file listing those variables available for reporting (on the MTR) for this particular simulation. Which meters are available for output depends on the actual simulation problem described in the IDF. A simulation with no chiller would not permit the output of any chiller report variables. The user may need to examine the RDD or MDD to find out which report variables are available in a particular simulation. The RDD and MDD are written only if the following is included in the IDF file.
A variant produces the same files in a IDF “ready” format.
dbg[LINK]
This is a text file containing debug output for use by EnergyPlus developers. Generally developers will add debug print statements wherever in the code that that they wish. There is a “standard” debug output that prints out conditions at all the HVAC nodes. This output is triggered by placing
in the IDF file. If Output:DebuggingData, 0 is entered, you will get an empty eplusout.dbg file.
dxf[LINK]
This is a file in AutoCad DXF format showing all the surfaces defined in the IDF file. It provides a means of viewing the building geometry. The DXF file from EnergyPlus highlights different building elements (shading, walls, subsurfaces) in differing colors. A number of programs can read and display DXF files. Output of this file is triggered by
in the IDF.
sln[LINK]
A text file containing the coordinates of the vertices of the surfaces in the IDF.
Output of this file is triggered by
Output:Reports, Surfaces, Lines;
in the IDF.
Postprocessing Program/Files[LINK]
A postprocessing program ReadVarsESO.exe is available that will read an ESO or MTR file and produce a file that can be read by Excel™. It can use an input file or not. In batch mode it is run by the little batch file RunReadESO.bat: Further information on this program is provided in the Input Output Reference under a section heading called “Using ReadVarsESO”.
Documentation content copyright © 1996-2026 The Board of Trustees of the University of Illinois and the Regents of the University of California through the Ernest Orlando Lawrence Berkeley National Laboratory. All rights reserved. EnergyPlus is a trademark of the US Department of Energy.
This documentation is made available under the EnergyPlus Open Source License v1.0.