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E4SMA supports its clients in assessing the flexibility of their power systems. This is a key consideration in planning for high shares of renewables, including maximum solar and wind power use.  To this end, we are operating the following power system models:



IRENA FlexTool

Flextoll is one of our preferred tools. It’s a power system model developed by IRENA with the VTT Technical Research Centre of Finland Ltd. FlexTool is a freely accessible, open-source modelling tool.

The FlexTool is data-driven and follows a relatively broad, general model structure. The user’s initial data largely determines what the model does. The inputs required for a FlexTool simulation include demand, the generation mix, hydrological data, time series for variable renewable sources, interconnections, and fuel costs. Transmission data can be divided into separate nodes to reflect real-world power system characteristics.


PyPSA (Python for Power System Analysis)

PyPSA is an open-source toolbox for simulating and optimizing modern power and energy systems. PyPSA is developed and maintained as a project by the Department of Digital Transformation in Energy Systems at the Technical University of Berlin. The purpose of the project is to provide a free, user-friendly, and performant model environment to support a smooth energy transition around the world.

The toolbox contains packages that are built in a modular sense so that they may be used independently from each other but interact easily. The packages enable energy planners to go all the way from calculating renewable energy potentials to creating complex electricity networks and cost-optimizing the pathway of a whole energy system.

PyPSA includes features such as unit commitment, variable wind, and solar generation, storage units, coupling to other energy sectors, and mixed alternating and direct current networks.

PyPSA is graph-based and designed to scale well with large networks and long time series.



Calliope is a free and open-source tool. It can be used to build energy system models at scales ranging from urban districts to entire continents.

By extensively using automated tests, it provides a solid foundation for building transparent and reproducible energy system models. The Calliope code is tested with a comprehensive suite of automated software tests and has been used in a large number of peer-reviewed publications. One example is the fully open-source model of the entire European energy system, Sector-Coupled Euro-Calliope.

Calliope provides interactive visualization of results from a model. The tool is available under an Apache 2.0 license.



The BALMOREL energy model is a partial equilibrium model. It supports modelling and analysis of the energy sector with an emphasis on the electricity and the combined heat and power sectors. The model has been developed, maintained, and distributed under open-source ideals since 2000. Hence, the model as well as project-generated information, including all details, can be freely downloaded.

The model development is mainly project-driven, with a user’ network and forum around it, supporting the open-source development idea. The BALMOREL model has been applied to projects in Denmark, Norway, Estonia, Latvia, Lithuania, and Germany, as well as in countries outside of Europe.

It has been used for analyses of the security of electricity supply, the role of demand response, wind power development, the role of natural gas, development of international electricity markets, market power, expansion of electricity transmission, international markets for green certificates, and emission trading as well as environmental policy evaluation, unit commitment, storage technologies, and learning curves.

The model is formulated in the GAMS modelling language and a GAMS license is needed to run the model. Additionally, it has a graphical user interface facilitating input data handling, output reporting, etc.



PLEXOS Integrated Energy Model is a simulation software designed for energy market analysis. The model can simulate developments of the electricity market. It can also integrate electric power, gas, heat and water. The simulations are based on mathematical programming.

The system supports various planning horizons from long-term to short-term, and several different time steps: the simulated time frames can range from minutes and hours to tens of years. The PLEXOS models can capture specifics of short-term operational limits, as well as the effects of system expansion.

The PLEXOS simulation platform is used by energy market participants, system planners, investors, regulators, consultants, and analysts worldwide.