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JSteam Documentation

JSteam is a high speed thermodynamic and modelling package for heat and power systems, with extensions to Excel, MATLAB and a C++ library. It is built on experience in the Oil & Gas Sector, as well as leveraging REFPROP for high speed, high accuracy thermodynamic and transport property calculations.

Previously JSteam Excel was sold as a commercial software package, however with limited time for support and development, it is now released purely as free (but not open source) software. It is still used in industries from Oil & Gas to Pulp & Paper and Power Generation and has proved highly accurate and robust for system modelling, case studies and optimization.

For most users the Excel interface is the recommended way to use JSteam. However the MATLAB interface has been used extensively within optimization work and is best suited for those familiar with MATLAB, or those looking for a thermodynamic library in MATLAB.

For more information on each interface, see the links below.

ExcelExcel Interface (Recommended)
MATLABMATLAB Interface
C++ libraryC++ Interface

News​

  • 20th July 2026

    The JSteam Wiki has been migrated to GitHub Pages, with improved navigation, search, and mobile support.

  • 23rd March 2023

    JSteam Toolbox is back! Recompiled and updated, and now even on GitHub!

  • 17th March 2023

    JSteam Excel is back! Recompiled and updated for the new website. Jump to the download page to start with the new free v3.26!