About EnergyPlus

Version 8.1.0
Updated December 31, 2013

EnergyPlus is an energy analysis and thermal load simulation program. Based on a user's description of a building from the perspective of the building's physical make-up and associated mechanical and other systems, EnergyPlus calculates heating and cooling loads necessary to maintain thermal control setpoints, conditions throughout a secondary HVAC system and coil loads, and the energy consumption of primary plant equipment. Simultaneous integration of these—and many other—details verify that the EnergyPlus simulation performs as would the real building.

Learn more by viewing a Webinar about building simulation, EnergyPlus, and OpenStudio Plug-in for SketchUp (WMV 11.5 MB). Download Windows Media Player. You can also read a text version of the audio and view the presentation slides.

EnergyPlus Key Capabilities

EnergyPlus logo

The following is a representative list of EnergyPlus capabilities:

  • Integrated, simultaneous solution where the building response and the primary and secondary systems are tightly coupled (iteration performed when necessary)

  • Sub-hourly, user-definable time steps for the interaction between the thermal zones and the environment; variable time steps for interactions between the thermal zones and the HVAC systems (automatically varied to ensure solution stability)

  • ASCII text based weather, input, and output files that include hourly or sub-hourly environmental conditions, and standard and user definable reports, respectively

  • Heat balance based solution technique for building thermal loads that allows for simultaneous calculation of radiant and convective effects at both in the interior and exterior surface during each time step

  • Transient heat conduction through building elements such as walls, roofs, floors, etc. using conduction transfer functions

  • Improved ground heat transfer modeling through links to three-dimensional finite difference ground models and simplified analytical techniques

  • Combined heat and mass transfer model that accounts for moisture adsorption/desorption either as a layer-by-layer integration into the conduction transfer functions or as an effective moisture penetration depth model (EMPD)

  • Thermal comfort models based on activity, inside dry bulb, humidity, etc.

  • Anisotropic sky model for improved calculation of diffuse solar on tilted surfaces

  • Advanced fenestration calculations including controllable window blinds, electrochromic glazings, layer-by-layer heat balances that allow proper assignment of solar energy absorbed by window panes, and a performance library for numerous commercially available windows

  • Daylighting controls including interior illuminance calculations, glare simulation and control, luminaire controls, and the effect of reduced artificial lighting on heating and cooling

  • Atmospheric pollution calculations that predict CO2, SOx, NOx, CO, particulate matter, and hydrocarbon production for both on site and remote energy conversion

EnergyPlus User Interface

EnergyPlus is a stand-alone simulation program without a 'user friendly' graphical interface. EnergyPlus reads input and writes output as text files. A number of graphical interfaces are available.