EnergyPlus is DOE’s whole-building energy simulation engine. EnergyPlus includes advanced simulation features including sub-hourly time steps, simultaneous solution of zone conditions and HVAC system actions, a modular HVAC structure that accommodates a wide range of system configurations, and a runtime scripting language for user-defined control strategies. Originally released in 2001, EnergyPlus is continually updated—major updates are released twice a year—and fully documented and supported. EnergyPlus is open source software. It forms the analytical basis for energy-efficiency standards such as ASHRAE 90.1 and for both free and commercial energy analysis products. Version 8.4.0 was released 9/30/2015. Learn more at energyplus.net.