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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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