An energy simulation program whose modular system approach makes it one of the most flexible tools available. TRNSYS (TRaNsient SYstem Simulation Program) includes a graphical interface, a simulation engine, and a library of components that range from various building models to standard HVAC equipment to renewable energy and emerging technologies. TRNSYS also includes a method for creating new components that do not exist in the standard package. This simulation package has been used for more than 30 years for HVAC analysis and sizing, multizone airflow analyses, electric power simulation, solar design, building thermal performance, analysis of control schemes, etc.

External Link to Product Page:
United States
Major Capabilities:
Whole Building Energy Simulation, Parametrics and Optimization
Building Type:
Subsystem Level, Commercial, Residential, Multi Family, Industrial, District Scale
Reduced for Non-Commercial/Academic Use
Help And Support:
Free Email Support
Last Software Update:
September 15, 2015
None to use standard package; FORTRAN knowledge helpful for developing new components.
Engineers, researchers, consulting firms, architects.
The TRNSYS input file, including building input description, characteristics of system components, manner in which components are interconnected, and separate weather data (supplied with program) are all ASCII files. All input files can be generated with a graphical user interface known as Simulation Studio. The envelope for the TRNSYS building can now be three-dimensionally created in the TRNSYS3D plugin for SketchUp™ and edited in the TRNBuild interface.
Basic output format is ASCII. The data included in those files can be life cycle costs; monthly summaries; annual results; histograms; plotting of desired variables (by time unit). It is also possible toplot variables online (as the simulation progresses).
Due to its modular approach, TRNSYS is extremely flexible for modeling a variety of energy systems in differing levels of complexity. Supplied source code and documentation provide an easy method for users to modify or add components not in the standard library; extensive documentation on component routines, including explanation, background, typical uses and governing equations; supplied time step, starting and stopping times allowing choice of modeling periods. The TRNSYS program includes a graphical interface to drag-and-drop components for creating input files (Simulation Studio), a utility for easily creating a building input file (TRNBuild), and a program for building TRNSYS-based applications for distribution to non-users (TRNEdit). Web-based library of additional components and frequent downloadable updates are also available to users. Extensive libraries of non standard components for TRNSYS are available commercially from TRNSYS distributors. TRNSYS also interfaces with various other simulation packages such as COMIS, CONTAM, EES, Excel, FLUENT, GenOpt and MATLAB.