Guide for Module Developers — EnergyPlus 9.6

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Data Services[LINK]

For the most part, modules are independent and only need the data they have within or USE from other modules. Occasionally, this may take on more complicated needs such as accessing “real-time” values for meters and/or custom meters or current report variable names/values.. Meter names are standard; you may have to use user input to get custom meter names.

Global variable: MetersHaveBeenInitialized[LINK]

Meters are a bit peculiar and aren’t fully set until the first run through the first time step of the HVAC simulation. Therefore, there is a global variable “MetersHaveBeenInitialized” which is set to true after meters have been set up. If you have a call to your routine that must use meter values as part of the simulation, you must use this variable before your items can be set.


If (MetersHaveBeenInitialized) CALL ManageDemand

Only the first time step will be missed in your routine and that time step will be part of “warming up” the simulation, so there is minimal impact due to this limitation.


You use the GetMeterIndex to check if a meter is valid for a particular simulation or if the user has entered a custom meter of that name. You use the index returned in later calls to get the value of the meter. Returns 0 if there is no meter of that name.



thismeter = GetMeterIndex(‘Electricity:Facility’)


This subroutine returns the variable type (real, integer, meter, etc.) (varType) whether it is an averaged or summed variable (varAvgSum), whether it is a zone or HVAC time step (varStepType), and the number of keynames for a given report variable or report meter name (varName). The variable type (varType) and number of keys (numKeys) are used when calling subroutine GetVariableKeys to obtain a list of the keynames for a particular variable and a corresponding list of indexes. An INTERFACE statement exists in the module OPInterfaces.


SUBROUTINE GetVariableKeyCountandType(varName, numKeys, varType, &

varAvgSum, varStepType, varUnits)


USE OPInterfaces, ONLY: GetVariableKeyCountAndType

! call the key count function but only need count during this pass

CALL GetVariableKeyCountandType(AlphArray(fldIndex), &





This subroutine returns a list of keynames and indexes associated with a particular report variable or report meter name (varName). This routine assumes that the variable type (real, integer, meter, etc.) may be determined by calling GetVariableKeyCountandType. The variable type and index can then be used with function GetInternalVariableValue to to retrieve the current value of a particular variable/keyname combination. An INTERFACE statement exists in the module OPInterfaces.


SUBROUTINE GetVariableKeys(varName,varType,keyNames,keyVarIndexes)


USE OPInterfaces, ONLY: GetVariableKeys

CALL GetVariableKeys(AlphArray(fldIndex), TypeVar, NamesOfKeys, &


! See earlier GetVariableKeyCountandType as well.


You use the GetCurrentMeterValue to obtain the value of a meter at its last “reported value” (timestep). Note that all meters are reported on the zone time step. Returns 0.0 if the MeterNumber passed is < = 0.


INTEGER, EXTERNAL :: GetCurrentMeterValue

thismetervalue = GetCurrentMeterValue(ElecFacilityMtrIndex)


You use the GetInstantMeterValue to get a component of a meter’s value by index type. The values returned are “raw” (that is, not weighted by time step values). In these calls, 1 is a zone time step index, 2 is a system time step index.


INTEGER, EXTERNAL :: GetInstantMeterValue

FuelType%ElecFacility = & GetInstantMeterValue(FuelType%ElecFacilityIndex,1)*FracTimeStepZone + &



This function returns the current value of the Internal Variable assigned to the varType and keyVarIndex. Values may be accessed for real and integer report variables and meter variables. The variable type (varType) may be determined by calling subroutine and GetVariableKeyCountandType. The index (keyVarIndex) may be determined by calling subroutine GetVariableKeys. To use, there is an INTERFACE statement in DataGlobals.f90


USE DataGlobals, ONLY: GetInternalVariableValue

curValue = GetInternalVariableValue(curTypeOfVar,curVarNum)