GTMax (Generation and Transmission Maximisation Model) simulates the dispatch of electric generating units and the economic trade of energy among utility companies using a network representation of the power grid [1]. It was created by Argonne National Laboratory in 1995 [2] and is currently at version 5.6. The model is used by universities, consultants, and power companies in about 25 countries, but the exact number of users is not known. Various licensing options are available to purchase GTMax, but prices can only be obtained by contacting Argonne National Laboratory [1]. To use the basic functions of GTMax, one week of training is required and to use the advanced features an additional week is necessary.

In GTMax, the generation and energy transactions serve electricity loads that are located at various locations throughout the simulated region, which is typically a national energy-system. The model can simulate both the electricity sector and district heating networks. All thermal, renewable and electric vehicles can be simulated by the model. All storage and conversion technologies that do not involve hydrogen can also be simulated: which are pumped-hydro, battery and compressed-air energy-storage. Links and transformers connect generation and energy delivery points to load centres. Electricity loads are satisfied, curtailed via contractual agreements, or not served due to a generator supply shortage or because of transmission limitations. The objective of GTMax is to maximise the net revenues of power systems by finding a solution that increases income while keeping expenses at a minimum. When multiple systems are simulated, GTMax identifies utilities and projects that can successfully compete on the open market. The model computes and tracks hourly energy transactions, market prices, and production costs. Using a mixed integer Linear Programming (LP) approach GTMax simultaneously solves the maximisation objective for all hourly time steps in a weekly simulation period. The model can be run for all 52-weeks in a year or for selected representative weeks. Simulated activities are driven by energy market forces and are performed within the physical and institutional constraints of the interconnected systems. Some limitations that are modelled include power plant seasonal and hourly maximum and minimum generation levels, limited energy constraints, contractual transmission capabilities, and terms specified in firm and IPP contracts. GTMax also considers detailed operational limitations such as power plant ramp rates and hydropower reservoir constraints. Firm transmission contracts, along with Transmission Reliability Margins (TRM) and Capacity Benefit Margins (CBM) are also factored into model simulations. GTMax computes Available Transmission Capabilities (ATC) for each transmission link, over Composite Transfer Capability (CTC) link groups and over user-specified pathways. Power flows in the model are computed using either a DC Optimal Power Flow (DCOPF) formulation or contractual power flow methodology. For several customers, the model is implemented in real-time operations with connections to SCADA systems.

GTMax has been used for a number of studies which are listed at [3]. Some examples are an investigation into a future regional electricity-market in South-eastern Europe [4], an evaluation of a new transmission interconnection between Ethiopia and Kenya [5], and also, to evaluate the effectiveness of using high flows from Glen Canyon Dam to improve natural, recreational, and cultural resources in Grand Canyon National Park [6].


  1. Generation and Transmission Maximization (GTMax) Model, Argonne National Laboratory, 23rd April 2009,
  2. Argonne National Laboratoty, U.S. Department of Energy, 23rd April 2009,
  3. Power Systems Analysis Program, Argonne National Laboratory, 23rd April 2009,
  4. Koritarov, V. S. & Veselka, T. D. Modeling the Regional Electricity Network in Southeast Europe. Argonne National Laboratory, 2005,
  5. Kostova, B., Poprea, L., Popescu, V. & Veselka, T. D., Simulation of Regional Power Markets in the Planning of Trans-Border Interconnections, Proc. of the IEEE PES PowerTech 2009, Bucharest, Romania, 28 June – 2 July.
  6. The Economic Cost of the March 2008 Glen Canyon “Flush”, Argonne National Laboratory, 23rd April 2009,