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Sébastien Léger


Specializes in the long-term evolution of the energy markets and technologies as the head of our integrated power markets modeling, leads the firm's Sustainability Practice in France, and coleads the regulatory strategy and water and waste work within our European Electric Power & Natural Gas Practice

Sébastien is a strategy specialist in the field of energy and infrastructure. He counsels his clients on investments and acquisitions, market analysis, technological and regulatory issues, public–private partnerships, and environmental and energy transformations. A partner in McKinsey’s Paris office, he previously worked in our London office.

Sébastien has contributed to several McKinsey R&D initiatives on environmental and energy issues, particularly in the area of renewable energies. He directed the prospective report Global Energy Perspectives 2050 and was co-rapporteur of the Montaigne Institute’s working group on smart grids.

In addition, Sébastien helps lead our work in integrated power-markets modeling and regulatory strategy for our Electric Power & Natural Gas Practice.

Examples of his recent client projects include the following:

  • conducting strategic due diligence on a water utility for a financial investor, which included analyzing key trends in local water markets, the impact of new regulation, and savings from further operational improvements, as well as identifying growth opportunities at home and abroad
  • supporting the merger of two water companies, including architecture and project-management office of the overall merger, definition of the new organization, and implementation of the value-creation management system
  • leading an innovation project to identify new business opportunities on a 5-year horizon on water and waste, including reviewing key trends and building business cases for priority opportunities
  • leading a project on circular economy, which included conducting a diagnostic versus international benchmarks and developing recommendations to boost the development of circular economy in France and abroad
  • developing a power model to assess the long-term evolution of power prices across multiple countries
  • assessing the competitiveness of nuclear-power generation against other generation technologies in several power markets leveraging, in part, long-run marginal cost of electricity
  • assessing the value of electricity generation assets in Europe leveraging McKinsey power model
  • developing a strategic perspective on the possible evolution of the gas demand and supply equilibrium in Europe and abroad for a natural-gas company
  • creating a renewable growth strategy for a leading European utility, including a detailed assessment of wind, solar, and biomass for each regional market
  • leading several due diligences and strategic review of renewable project developers, including market scan and growth options
  • assessing the wood-based biomass value chain in a European country and defining an entry strategy
  • assisting a European distribution company in defining its smart-grid strategy
  • developing the governance, business model, and business plan of the clean-technology business of an industrial player

Published work

Sustainability in packaging: Global regulatory development across 30 countries”, McKinsey & Company, February 2022

Réussir la transition de l'Europe vers la neutralité carbone”, McKinsey & Company, Juillet 2021

Anticiper la crise d’après”, McKinsey & Company, Juillet 2020

How utilities can keep the lights on,” McKinsey & Company, May 2018

A framework for fostering effective energy transitions,” McKinsey & Company, April 2018

What if the latest wind and solar auction results were the new reality of electricity prices?,” McKinsey & Company, March 2018

Can carbon prices fire up gas demand in electricity generation?”, McKinsey & Company, Janvier 2018

Beyond the storm--value growth in the EU power sector”, McKinsey & Company, Avril 2015


DIAGMA International
Logistics and Supply Chain Management consultant

L’Oréal Indonésia
Project manager and responsible for quality assurance


École Centrale de Paris
MSc, engineering