TRNSYS

What TRNSYS does

TRNSYS is a component-based transient system simulation software environment developed and distributed by Thermal Energy System Specialists, LLC (TESS), a privately held LLC headquartered in Madison, Wisconsin. The product is used primarily to model transient (time-varying) behavior of thermal and electrical energy systems, with secondary applications in traffic flow and biological processes. Its user base spans building simulation professionals, HVAC and mechanical engineers, renewable-energy researchers, academic institutions, and power-plant engineers worldwide. Approximately 150 standard component models ship with the core package, supplemented by 14 add-on TESS Libraries containing over 250 specialized components and a community-contributed TRNLIB of user-developed models.

The underlying technology is a Fortran-based kernel compiled as a Windows DLL, paired with a graphical front-end (Simulation Studio), a building-geometry interface (TRNBuild with the SketchUp-based TRNSYS3D plugin), a Fortran development environment (TypeStudio), a text editor (TRNEdit), and an application-packaging tool (TRNSED). The architecture is open and extensible: users can write custom components in Fortran, C, C++, or the in-product W language, then package and distribute them as standalone applications. Auxiliary integrations include LBNL's GenOpt optimization program (TRNOPT) and the COMIS multi-zone air-flow model (TRNFlow).

Commercially, TESS pursues a perpetual-license model with no annual maintenance fees, separate commercial and educational pricing tiers, multi-user license packs (single user to 50+ users), and major-version upgrades on roughly five-year cycles. Distribution is dual-track: direct enterprise sales from Madison plus 11 official international distributors — including exclusive partners in the U.S., France (CSTB), Germany (Transsolar), Spain, and Portugal — many of whom also co-develop core TRNSYS tooling. The company has operated since 1975 without external institutional funding and currently employs 11-50 people.

Name

TRNSYS

Legal name

Thermal Energy System Specialists, LLC

Website

https://trnsys.com

Company type

Private

Founded year

1975

Operating status

Operating

Headcount range

11–50 employees

Short description

TRNSYS, developed by Thermal Energy System Specialists (TESS) in Madison, Wisconsin, is a Fortran-based transient simulation environment with ~150 standard and 250+ add-on component models for thermal and electrical energy systems. It serves researchers, engineers, consultants, and academic institutions worldwide via perpetual licenses and 11 international distributors.

Ownership category

akta.pro rank

Headquarters

HQ city

Madison

HQ country

United States

HQ region

North America

Offices2 records

Markets served

GTM type

B2B

Offering type

Software

Cost components

Personnel, Technology or R&D, Marketing or Sales, Operations

Revenue model

1. TRNSYS Software Licenses: Perpetual license model with free minor version updates (approximately annually within major version). Paid major version upgrades approximately every five years. Single user and multi-user license tiers (5, 10, 20, 30, 40, 50 users). No annual maintenance fees. Separate pricing for commercial and educational institutions.
2. TESS Component Libraries Add-ons: Add-on component libraries purchased separately. 14 different libraries available with discounts for purchasing multiple libraries (25% off for 5-9, 35% off for 10-13, 50% off for all 14). Upgrade pricing available. Libraries include Application, Cogeneration, Controls, Electrical, Ground Coupling, GHP, High Temp Solar, HVAC, Hydronics, Loads and Structures, Optimization, Solar Collector, Storage Tank, and Utility components.
3. Individual Component Sales: Complex single TRNSYS components available for individual purchase. Components sold with various combinations of source code, DLL, proformas, technical documentation, examples, and sample catalog data. Prices range from $100 to $500 per component.
4. TRNFlow: Air flow modeling add-on for TRNSYS. Sold as a separate product with perpetual license and free online updates.

Pricing tiers

Go-to-market motion3 records

Distribution channels3 records

Marketing channels7 records

Core offering

TRNSYS is a component-based, graphically driven transient system simulation software environment used to model the behavior of thermal and electrical energy systems. It consists of a Fortran-based kernel/engine that iteratively solves systems and determines convergence, plus an extensive library of approximately 150 standard component models spanning pumps, multizone buildings, HVAC equipment, solar thermal, wind, electrolyzers, and emerging technologies. The software is delivered with a suite of tools (Simulation Studio, TRNBuild, TRNEdit, TypeStudio, TRNSYS3D, TRNSED) and is augmented by 14 add-on TESS Component Libraries containing over 250 specialized components.

Product overview

TRNSYS is a component-based transient system simulation software environment used primarily for thermal and electrical energy systems modeling. The core product (TRNSYS 18) consists of a kernel engine plus approximately 150 standard component models, delivered through a suite of tools: Simulation Studio (graphical front-end), TRNBuild (building model interface), TRNEdit (text editor), TypeStudio (Fortran development environment), TRNSYS3D (SketchUp plugin), and TRNSED (application distribution tool). This core platform is augmented by add-on TESS Component Libraries — 14 distinct libraries containing over 250 specialized components covering applications from solar collectors and HVAC to ground coupling, cogeneration, and electrical/PV systems. An additional tool, TRNFlow, integrates COMIS air flow modeling with the building model. Users can purchase individual specialized components separately. The architecture is extensible: users can write custom components in Fortran, C, C++, or the TRNSYS W language. The product runs on Windows and includes free technical support with permanent licenses.

Differentiator

Problem solved

Functional benefit

Brands

• TESS Component Libraries: Add-on component libraries for TRNSYS containing over 250 components across 14 different libraries including Application, Cogeneration, Controls, Electrical, Ground Coupling, Geothermal Heat Pump, High Temperature Solar, HVAC, Hydronics, Loads and Structures, Optimization, Solar Collector, Storage Tank, and Utility components.

Products and services

• TRNSYS Simulation Studio Graphical front-end environment for assembling detailed transient system simulations by connecting component outputs to inputs graphically, with online plotting of any system variable during simulation. Included with TRNSYS 18 core license.
• TRNBuild Graphical interface for creating and editing non-geometry information required by the TRNSYS Building Model, including wall/layer material properties, ventilation/infiltration profiles, gains, radiant ceilings/floors, and occupant positioning for comfort calculations.
• TypeStudio
• TRNEdit
• TRNSYS3D
• TRNSED
• TRNFlow
• HVAC Equipment Component Library
• Cogeneration (CHP) Component Library
• Geothermal Heat Pump (GHP) Component Library
• Solar Collector Component Library
• Optimization Component Library (TRNOPT)
• Individual TRNSYS Components
• TRNSYS Academy Self-Paced Online Training Self-paced online training solution sequenced to guide users from basics through entry-level TRNSYS concepts and projects, available via TRNSYS Academy and included with TRNSYS 18 purchase.

Quantifiable outcome

• 40+ years of commercial availability demonstrating sustained market need and continuous improvement
• +1 more outcomes

Segments5 records

Ideal customer profiles5 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Integration3 records

Feature7 records

Partnerships

Five partnerships are on record, tiered core and moderate.

• CSTB (Centre Scientifique et Technique du Bâtiment)coreTechnology or IntegrationFrench distributor and developer of Simulation Studio - the graphical front end to TRNSYS. CSTB contributes to TRNSYS development as a key technology partner.
• TranssolarcoreChannel Partner/ Reseller/ DistributorGerman distributor and developer of TRNBUILD graphical building description processor. Transsolar has developed non-standard TRNSYS components for German users.
• Solar Energy Laboratory at University of WisconsincoreStrategic or Co-development PartnerMaintains the informational (non-commercial) TRNSYS website at sel.me.wisc.edu. Historical home of TRNSYS development.
• IBPSA (International Building Performance Simulation Association)moderateGTM or Marketing PartnerTESS participates in IBPSA-USA, IBPSA-Canada, and IBPSA-International conferences with one-day training workshops and live-taught online classes.
• Lawrence Berkeley National LaboratorycoreTechnology or IntegrationTRNSYS Optimization Library (TRNOPT) couples TRNSYS simulation with LBNL's GenOpt program for cost/error function minimization and simulation calibration.

Scale indicators6 records

Recent moves6 records

Expansion highlights5 records

Direct peers

• EnergyPlus: U.S. Department of Energy-sponsored building energy simulation program. Directly competes with TRNSYS for whole-building energy modeling and is free, which heavily pressures TRNSYS's pricing in academic and budget-constrained segments.
• IES VE (Integrated Environmental Solutions): Commercial building performance analysis suite covering energy, daylighting, CFD, and HVAC. Competes directly with TRNSYS in the integrated building simulation market, particularly with engineers and consultants specifying energy modeling software for commercial projects.
• DesignBuilder: GUI front-end and enhanced workflow layer for EnergyPlus targeting building energy consultants. Competes for the same building simulation professional segment that uses TRNSYS for coupled thermal/airflow analysis.
• OpenStudio: NREL-developed open-source toolkit for EnergyPlus modeling. A free alternative that competes for energy modelers' attention and is increasingly integrated with parametric and optimization workflows, eroding TRNSYS's value proposition in standard building energy analysis.
• eQUEST: Free building energy analysis tool built on EnergyPlus/DOE-2 with a simplified interface. Competes at the entry-level and educational end of the market where TRNSYS also sells heavily-discounted educational licenses.
• ESP-r: Research-grade transient building simulation tool developed at the University of Strathclyde. Overlaps with TRNSYS in coupled thermal/airflow modeling and is widely used in academic energy research, competing for the same researcher customer base.

Emerging players

• Modelica Association / Modelica Libraries: Open-source equation-based modeling language for physical systems with strong energy, HVAC, and building libraries (e.g., Buildings library from LBNL). Represents an emerging open standard that could subsume some transient energy simulation use cases currently served by TRNSYS.

Broad incumbents

• Dassault Systèmes Dymola: Commercial Modelica-based multi-engineering modeling environment from Dassault Systèmes. Offers overlapping capability for transient energy system modeling as part of a much broader CAE portfolio, with stronger enterprise sales channels and integration into the 3DEXPERIENCE platform.
• MathWorks Simulink: Block-diagram simulation environment widely used in energy systems, controls, and HVAC research. Competes for the same engineering audience as TRNSYS but from a much broader platform with deep academic adoption, MATLAB integration, and large R&D budget.
• COMSOL Multiphysics: General-purpose multiphysics simulation platform with add-on modules for heat transfer, CFD, and structural analysis. Competes for engineering simulation budget at the same universities and research labs that adopt TRNSYS, with stronger cross-discipline positioning.

Market position

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

• YouTubeyoutube.com/channel/UCiuW9mivuCC67xl2VuIKyPg
• Facebookfacebook.com/TRNSYS
• LinkedInlinkedin.com/groups/TRNSYS-3325945

Revenue estimate

Valuation estimate

Number of profiles

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about TRNSYS