EnergyPlus

EnergyPlus
Name	EnergyPlus
Title	EnergyPlus
Developer	United States Department of Energy; Department of Energy national laboratories; private collaborators
Released	2001
Latest release	ongoing
Programming language	Fortran; C++
Operating system	Microsoft Windows; Linux; macOS
License	Open-source software

EnergyPlus is a building energy simulation program used to model heating, cooling, lighting, ventilation, and other energy flows in buildings. It is widely employed by researchers, practitioners, and agencies to evaluate energy performance, inform building codes, and support green building certification programs. EnergyPlus integrates detailed physical models for heat transfer, fluid flow, and controls to predict hourly and sub-hourly energy use for complex building systems.

Overview

EnergyPlus simulates building energy use across time scales relevant to ASHRAE standards and national building codes such as the International Energy Conservation Code and programs like Leadership in Energy and Environmental Design. It combines thermal zone models, plant loop models, airflow network models, and advanced controls to represent interactions among HVAC equipment, envelope, and internal loads. Users employ EnergyPlus for compliance demonstrations, retrofit analysis, parametric studies, and research supporting agencies such as the National Renewable Energy Laboratory, Lawrence Berkeley National Laboratory, and the Pacific Northwest National Laboratory.

Development and History

EnergyPlus originated as a successor to legacy tools developed by Lawrence Berkeley National Laboratory, University of Illinois at Urbana–Champaign collaborators, and codebases used by Oak Ridge National Laboratory and the National Institute of Standards and Technology. The project consolidated models from programs like BLAST and DOE-2 into a new simulation engine released under DOE stewardship in the early 2000s. Over successive releases the codebase incorporated contributions from international partners including Natural Resources Canada, European research institutes, and industry vendors, aligning with standards such as ASHRAE Standard 140 and responding to policy needs from entities like the United States Department of Energy and the European Commission.

Features and Capabilities

EnergyPlus includes detailed models for HVAC equipment such as air handling units, chillers, boilers, heat pumps, variable refrigerant flow systems, and thermal storage systems used in projects by firms working with American Society of Heating, Refrigerating and Air-Conditioning Engineers guidelines. It simulates building envelope conduction, convection, and radiation using methods compatible with International Organization for Standardization and ASHRAE procedures. The program handles advanced fenestration and shading devices, daylighting systems for integration with controls, occupant schedules and internal gains, and plant loop hydraulics for combined heat and power and district energy network studies relevant to United Kingdom and Japan urban planning initiatives.

Architecture and Simulation Engine

The EnergyPlus architecture separates a zone air heat balance solver, surface heat balance, and plant-loop hydraulic solver into modular components, enabling coupling with control algorithms derived from research at Massachusetts Institute of Technology and Stanford University. The engine executes time-step integrations, including variable sub-hourly simulation, dynamic building envelope models, and coupled moisture transfer, supporting verification with benchmarks such as ASHRAE Standard 140 and comparisons with models from CIBSE. Code contributions in Fortran and C++ facilitate cross-platform compilation for Linux and macOS environments used in academic clusters and cloud computing by institutions like Google and Amazon Web Services for large-scale parametric studies.

Validation, Accuracy, and Use Cases

Validation efforts for EnergyPlus have included inter-model comparisons, field measurements in demonstration buildings tied to projects by National Renewable Energy Laboratory and Lawrence Berkeley National Laboratory, and regulatory acceptance in programs administered by Department of Energy offices. Use cases span envelope retrofit evaluation for municipal programs in cities like New York City and London, life-cycle cost analysis for campuses such as Harvard University and University of California, Berkeley, and renewable integration studies tied to European Union energy transition initiatives. Peer-reviewed studies in journals and conference proceedings from ASHRAE, International Building Performance Simulation Association, and IEEE document accuracy across diverse climates and system configurations.

Integration, Interfaces, and Extensions

EnergyPlus supports interoperability with building information modeling platforms including Autodesk Revit and model translation efforts like gbXML and IFC handled by organizations such as buildingSMART. Scripting and parametric workflows utilize wrappers and tools developed by communities around Python bindings, plugin frameworks used by OpenStudio and integrations with optimization tools from MATLAB and GAMS. Coupling with computational fluid dynamics packages from vendors and projects at institutions like ETH Zurich and Delft University of Technology enables multi-scale modeling for advanced ventilation and indoor air quality studies.

Adoption, Community, and Licensing

EnergyPlus is distributed under an open-source license overseen by the United States Department of Energy and supported by a global developer community including national laboratories, universities, and commercial consultancies such as those participating in DOE’s Building Technologies Office initiatives. Training, user support, and conferences are organized through events by IBPSA and regional chapters of ASHRAE, with extensive user-contributed libraries, example models, and plugin ecosystems maintained on platforms used by GitHub and research repositories affiliated with institutions like Carnegie Mellon University. Category:Building energy simulation software