EnergyPlus™ is a building energy simulation program used by engineers, architects, and researchers to model energy consumption in buildings, including heating, cooling, ventilation, lighting, plug and process loads, and water use.

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EnergyPlus is free, open-source, and cross-platform—it runs on the Windows, Mac OS X, and Linux operating systems. Its development is funded by the U.S. Department of Energy’s (DOE) Building Technologies Office (BTO). Along with OpenStudio, EnergyPlus is part of BTO’s building energy modeling program portfolio.