# EnergyPlus Errors EnergyPlus errors occur time to time. Here is a practical reference for the errors you'll actually encounter. Organized roughly by when they appear in a typical modeling workflow. ### Simulation Control & Weather | EnergyPlus Error | Description | Solution | | ------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | SimulationControl object required but not found | No top-level control object telling EnergyPlus what to run (design days, annual simulation, sizing) | Add a SimulationControl object. It should be near the top of your IDF. Enable at minimum "Run Simulation for Sizing Periods" or "Run Simulation for Weather File Run Periods" | | Requested Sizing Calculation but no sizing run in SimulationControl | Objects set to autosize but you haven't enabled sizing period calculations | In SimulationControl, set "Do Zone Sizing Calculation" and "Do System Sizing Calculation" to Yes | | Weather file cannot be opened | EnergyPlus can't find the EPW file at the path you specified | Check the file path in your weather file object. Use absolute paths if relative paths aren't resolving. Verify the file actually exists | | Unrecognized weather file format | File isn't in EPW format or is corrupted | Use only EPW format weather files. If converting from TMY2 or other formats, use the Weather Converter utility | | Solar radiation values exceed extraterrestrial maximum | Weather data has impossible solar values, usually from corruption or unit errors | Inspect the weather file in a text editor. Look for radiation values over 1400 W/m². Either fix the file or get a clean version | | Ground temperatures not provided | Missing ground temps for slab or basement heat transfer | Add Site:GroundTemperature:BuildingSurface object with monthly temperatures, or use the Slab or Basement preprocessor tools | ### Geometry Errors | EnergyPlus Error | Description | Solution | | ----------------------------------------------------------------------- | ---------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------- | | Surfaces do not enclose a convex zone volume | Zone geometry folds back on itself or is concave | Split complex zones into multiple convex zones. L-shaped rooms need to be two zones, not one | | Surface vertices not in same plane (within tolerance) | Four or more points defining a surface don't lie flat | Break warped surfaces into smaller planar facets. This usually happens on import from CAD with curved elements | | Outward facing angles of subsurface differ from base surface | Window or door isn't parallel to its parent wall | Check subsurface vertex coordinates. Rotate the subsurface to match the base surface normal, or reimport from your geometry tool | | Calculated Zone Volume significantly different from user-entered volume | Volume from surface geometry doesn't match what you typed in the Zone object | Let EnergyPlus calculate the volume (leave it blank in the Zone object), or fix your surface geometry to match | | Zone floor area is zero | No surface designated as a floor, or floor marked as different surface type | Designate at least one surface as a floor with the correct Outside Boundary Condition. Check your Surface objects for proper type assignment | | Surface has area less than minimum | Surface is absurdly small, typically under 0.01 m² | Delete the surface if it's a modeling error, or combine it with adjacent surfaces. These usually come from geometry cleanup issues | | Base surface has no zone | Surface exists but isn't assigned to any zone | Assign the surface to a zone in the Surface object, or delete it if it's orphaned from model edits | ### Material & Construction Errors | EnergyPlus Error | Description | Solution | | ---------------------------------------------------------- | ---------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------- | | CheckUsedConstructions: No constructions defined | Constructions exist in the file but aren't assigned to any surfaces | Assign constructions to surfaces in your BuildingSurface:Detailed objects, or delete unused construction definitions | | Material properties out of reasonable range | Density, conductivity, or specific heat values are physically impossible | Check material properties against reference data. Common issue: mixing metric and imperial units, or decimal point errors | | Material conductivity unreasonably low/high | Thermal conductivity below 0.005 or absurdly high | Verify conductivity units are W/m-K. Typical range: 0.02 (insulation) to 50 (metals). Fix obvious errors or use standard material properties | | Material thickness too small for stability | Layer under 3mm thick causes numerical instability | Combine very thin layers with adjacent materials, or use Material:NoMass for things like paint or vapor barriers | | WindowMaterial:Glazing invalid solar/visible transmittance | Glass properties violate physics (transmittance over 1.0 or visible > solar) | Use manufacturer data or LBNL Window database values. Visible transmittance can't exceed solar transmittance by much | | Construction has no interior or exterior layer | Empty or incomplete construction assembly | Add material layers to the Construction object. Every construction needs at least one layer | | Material:NoMass with negative thermal resistance | R-value is negative, which is impossible | Fix the sign. Thermal resistance is always positive. Check if you accidentally entered a U-value instead | ### Schedule Errors | EnergyPlus Error | Description | Solution | | --------------------------------------------------------------- | ------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------- | | Schedule values exceed specified range | Schedule has values outside its defined ScheduleTypeLimits bounds | Either fix the schedule values or change the ScheduleTypeLimits. Fractions must be 0 to 1, temperatures have different bounds | | GetScheduleType: Schedule type not defined | Referenced a ScheduleTypeLimits object that doesn't exist | Create the missing ScheduleTypeLimits object, or change the schedule to reference one that exists | | Schedule:Compact invalid number after Until | Syntax error in compact schedule (missing comma, wrong date format, typo) | Check the compact schedule syntax carefully. Common: "Until: 24:00" not "Until 24:00", and values must be comma-separated | | GetScheduleDayIntervalData: Intervals do not add up to 24 hours | Day schedule has gaps, overlaps, or doesn't end at 24:00 | Make sure Until: times span from 00:00 to 24:00 with no gaps. Last entry must be "Until: 24:00" | | Schedule:File - File not found or cannot be opened | External CSV schedule file is missing or has wrong path | Verify the file path. Use absolute paths if needed. Check file permissions and that it's actually a CSV | ### Internal Gains | EnergyPlus Error | Description | Solution | | ------------------------------------------------------ | ---------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- | | People definition causes more than 3 met per person | Activity level exceeds vigorous exercise (probably a unit error) | Check if you entered W/person instead of met. Typical office: 1.0-1.2 met, heavy work: 2.0-3.0 met | | Lights definition causes more than 100 W/m² | Lighting power density is absurdly high for typical buildings | Verify units are W/m² not W/zone. Typical office: 8-12 W/m², warehouse: 5-8 W/m² | | ElectricEquipment definition exceeds reasonable limits | Equipment load seems too high for the space | Check if you entered total watts instead of W/m². Or verify this is actually a data center or industrial space | ### HVAC System Topology | EnergyPlus Error | Description | Solution | | ----------------------------------------------------- | -------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | | Plant loop has no demand components | Created a water loop but nothing uses it | Add coils, baseboards, or other demand equipment to the demand side. Or delete the unused loop | | Plant loop has no supply components | Have demand equipment but no chillers, boilers, or other supply | Add supply equipment (chiller, boiler, district heating/cooling). Every loop needs both supply and demand sides | | Plant/Condenser Loop topology inconsistent | Supply and demand sides aren't connected properly, or branches don't close | Check that supply outlet connects to demand inlet and demand outlet connects to supply inlet. Verify all branches form closed loops | | Plant Component on demand side of two different loops | Same equipment connected to multiple loops incorrectly | Use HeatExchanger:FluidToFluid to transfer between loops. Don't directly connect a coil to two different plant loops | | AirLoopHVAC has no supply fan | Air system missing required fan object | Add a Fan:ConstantVolume, Fan:VariableVolume, or Fan:OnOff object to the supply side | | Missing heating coil in AirLoopHVAC | Air system has cooling but no heating, and the climate needs it | Add a heating coil even if loads are minimal. Use a small electric resistance heater if nothing else | ### HVAC Sizing Issues | EnergyPlus Error | Description | Solution | | -------------------------------------------------------- | ------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | SizingPlant: Calculated loop capacity is zero | Autosizing found no load on the design day | Check that design days create heating/cooling loads. Verify zones connected to this loop actually need conditioning. May need to create design days with more extreme conditions | | SizingSystem: Heating/Cooling coil sizing failed | Zone loads too small for autosizing to work | Hardsize the coil capacity, or check that zone constructions and internal gains create realistic loads on design days | | Sizing:System object required but missing | Autosizing air system components without sizing parameters | Add Sizing:System object specifying supply air temperatures, humidity ratios, and other design parameters | | Sizing:Zone object required but missing | Autosizing zone equipment without zone sizing data | Add Sizing:Zone objects for each zone, or use Zone Sizing objects to define outdoor air requirements and design conditions | | Zone terminal unit maximum flow exceeds zone design flow | Individual terminal sized larger than the zone needs | Check zone sizing results. Either reduce terminal size or increase zone loads to justify the terminal capacity | | Sum of zone terminal flows exceeds air loop design flow | Terminals collectively demand more than the air handler can provide | Increase air handler capacity, or reduce terminal sizing. This creates a diversity problem where not all zones get full flow simultaneously | ### Zone HVAC & Controls | EnergyPlus Error | Description | Solution | | ------------------------------------------------ | -------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- | | Zone has no thermostat | HVAC equipment in zone but no temperature control | Add ZoneControl:Thermostat with heating and cooling setpoint schedules | | Thermostat references undefined schedule | Setpoint schedule doesn't exist | Create the missing schedule or fix the reference in the thermostat object | | Zone has multiple thermostat objects | More than one thermostat assigned to a single zone | Keep only one ZoneControl:Thermostat per zone. If you need different setpoints at different times, use schedule logic | | ZoneHVAC equipment not connected to zone node | Equipment exists but air connections are wrong | Check that zone inlet/outlet nodes in the equipment object match the zone's node names | | Zone equipment list contains undefined equipment | ZoneHVAC:EquipmentList references equipment that doesn't exist | Remove the reference from the equipment list, or create the missing equipment object | ### Coil & Equipment Errors | EnergyPlus Error | Description | Solution | | ------------------------------------------------------- | ----------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- | | Controller:WaterCoil maximum iterations exceeded | Water coil controller can't converge on a solution | Reduce controller gain (typically to 0.1-0.5). Or check that coil capacity is appropriate for the load | | Coil:Cooling:DX cycling ratio calculation failed | DX unit can't figure out how long to run to meet the load | Check part-load performance curves. Verify coil capacity is reasonable for the load. May need to adjust curve coefficients | | Coil outlet temperature exceeds maximum limit | Coil producing impossible temperatures | Check coil capacity and inlet conditions. Heating coils might be oversized, cooling coils might be undersized or seeing unrealistic loads | | DX coil curve coefficients produce negative performance | Performance curves predict negative capacity or COP in some operating range | Refit the curves using manufacturer data. Make sure curves are valid over the full operating range (temperatures, part-load ratios) | | Coil:Heating:Electric exceeds 100 kW | Electric resistance heat is very large (probably intentional, but EnergyPlus is checking) | Confirm this is correct. If intentional for a large space, you can ignore the warning. If it's a residential zone, you've got a problem | | Heat exchanger has negative effectiveness | Impossible heat exchanger performance (effectiveness must be 0 to 1) | Check supply and exhaust temperatures. Make sure you haven't swapped inlet and outlet temperatures in the object | ### Plant Equipment | EnergyPlus Error | Description | Solution | | ------------------------------------------------- | -------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- | | Chiller:Electric:EIR has zero reference capacity | Autosizing determined no capacity needed | Verify loop has cooling load on design day. Check that demand side equipment is connected and has loads | | Boiler efficiency exceeds 1.0 | Entered a COP value instead of efficiency, or have a typo | Boiler efficiency is always less than 1.0 (typically 0.75-0.95). If you have a heat pump, use different object type | | Cooling tower has no water flow | Tower connected but no water circulating | Check pump operation and that condenser loop is properly connected to supply equipment (typically a chiller) | | Pump power exceeds reasonable limit for flow rate | Pump curve or nominal power produces impossible specific power | Typical pumps: 0.1-0.5 kW per m³/h. Check pump total head and motor efficiency. Values should be realistic for the system | ### Setpoint Managers | EnergyPlus Error | Description | Solution | | ------------------------------------------------------------- | --------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | | No setpoint manager assigned to node | Node requiring temperature control has no setpoint manager | Add a SetpointManager (Scheduled, OutdoorAirReset, or other type) to control this node. Supply air and water nodes typically need setpoints | | SetpointManager:Scheduled has conflicting setpoints | Multiple setpoint managers trying to control the same node | Remove duplicate setpoint managers. Each node should have exactly one setpoint manager | | SetpointManager:OutdoorAirReset has invalid temperature range | Reset logic produces impossible temperatures or min exceeds max | Check that min/max setpoint temperatures are in the right order and physically reasonable for the system | ### Convergence & Numerical Problems | EnergyPlus Error | Description | Solution | | ---------------------------------------------------------- | --------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | | CalcZoneAirTempAndHumidity: Zone temperature out of bounds | Zone temperature outside reasonable limits (typically -100°C to 200°C) | Check for undersized equipment, missing insulation, or unrealistic internal gains. Review zone heat balance inputs | | System timestep reduced due to convergence failure | HVAC calculations couldn't converge, so EnergyPlus reduced timestep automatically | Review the .err file for related warnings. Common causes: unstable controls, poorly sized equipment, or extreme loads. Results may be questionable | | Warmup convergence not achieved | Initial conditions haven't stabilized before the simulation starts | Increase warmup days in SimulationControl (try 25 or more). For buildings with high thermal mass, this can take a while | | Autosizing calculation failed to converge | Sizing algorithm couldn't find stable equipment capacity | Hardsize some equipment to break circular dependencies. Complex systems with many autosized components can be unstable | ### Airflow Network | EnergyPlus Error | Description | Solution | | ------------------------------------------------------- | ------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------- | | AirflowNetwork:SimulationControl not found | Defined airflow network objects but haven't enabled the simulation | Add AirflowNetwork:SimulationControl and set control type (MultizoneWithDistribution or other option) | | AirflowNetwork:MultiZone:Zone not defined for all zones | Some zones in the model aren't included in the airflow network | Either add all zones to the network or reconsider whether you need multizone airflow modeling | | AirflowNetwork linkage has zero flow coefficient | Connection defined but has no flow capacity | Assign a realistic flow coefficient. For cracks: 0.001-0.01, for large openings: 0.5-1.0, depending on geometry | | Stack effect calculation failed to converge | Pressure/flow iteration couldn't stabilize | Reduce the convergence tolerance, or check for extreme temperature differences or very tall buildings creating unrealistic pressure gradients | ### Daylighting | EnergyPlus Error | Description | Solution | | ------------------------------------------------ | --------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- | | Daylighting:Controls references undefined window | Sensor trying to use a window that doesn't exist in the zone | Verify window names match exactly. Check that windows are in the same zone as the daylighting sensor | | Daylighting sensor outside zone geometry | Reference point coordinates don't fall within the zone volume | Recalculate sensor coordinates to ensure they're inside the zone. Check zone vertex coordinates and sensor XYZ values | | Illuminance map has invalid spacing | Grid spacing creates overlapping points or extends outside zone | Adjust X/Y spacing and origin coordinates so the grid fits entirely within the zone floor area | ### Output & Reporting | EnergyPlus Error | Description | Solution | | ----------------------------------- | ------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | | Output:Variable not found | Requested variable doesn't exist or is misspelled | Check the .rdd file after a successful run for available variable names. Copy-paste to avoid typos | | Meter not found | Energy meter doesn't exist because no equipment feeds into it | Verify you have equipment that reports to this meter. Or check the .mdd file for available meters | | Too many output variables requested | Requested so many outputs that file size is unmanageable | Reduce output variables to only what you actually need. Use Output:Diagnostics to disable debugging outputs | --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.betterbuilding.io/support-and-training/other-support/faqs/energyplus/energyplus-errors.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.