EnergyPlus is DOE’s flagship Building Energy Modeling tool. Replacing the DOE-2 engine, EnergyPlus provides more accuracy, fewer workarounds, and enables the analysis of more innovative and complex mechanical system and building designs.
eQUEST is the DOE 2 engine with wizards and graphics built on top of it. eQUEST is the most popular energy modeling program in existence. It's used by energy modelers and engineers all over the world. One big contributing factor to it's popularity is its cost, FREE, and the fact that it's built on the DOE 2 simulation engine. The other benefit of eQUEST is that it can be used at ever stage of building development, from the early designs to final stages.
Simergy is the newly developed graphic interface for EnergyPlus, affording more user-types the ability to analyze design performance at different stages in the design process. In addition to analyzing alternatives related to building form, glazing percentage/type, exterior shading, and aspects of daylighting at early stages of design, Simergy also allows high performance HVAC systems to be effectively included.
Trane Air Conditioning Economics, or TRACE, is a design and analysis tool developed to help professionals optimize the design of a building’s heating, ventilating, and air-conditioning system based on energy utilization and life-cycle cost.
TRNSYS is a simulation program primarily used in the fields of renewable energy engineering and building simulation for passive as well as active solar design. TRNSYS is a commercial software package developed at the University of Wisconsin.