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Portrait ofKostadin Sirleshtov

Kostadin Sirleshtov

Managing Partner
CEE Head of Energy & Climate Change

CMS Sofia
Landmark Centre
14 Tsar Osvoboditel Blvd.
Floor 1, 2
1000 Sofia
Languages Bulgarian, English

Kostadin Sirleshtov is managing partner of CMS Sofia and Head of Energy & Climate Change for CEE, where his team consists of over 80 lawyers in seven CEE jurisdictions.

His areas of expertise cover conventional power, renewables, oil & gas, infrastructure, projects, PPP, public procurement, and underground resources. He has worked as the Chief of the Minister’s cabinet for the Ministry of Energy and Energy Resources. Kostadin has over 25 years’ experience in the energy sector and is one of the most renowned energy experts in Bulgaria and in the wider CEE region.

Kostadin has vast experience in the electricity and oil & gas sector. He has represented clients, including renewables organisations, in negotiations with the Bulgarian Government, the National Electricity Company and the Electricity Transmission System Operator. In addition, he has advised major international oil & gas prospecting and exploration companies in Bulgaria on major onshore and offshore projects. He is particularly focused on advising renewables companies on the development, operation and acquisition, sale and financing of their projects in Bulgaria and CEE, including on litigation matters. Kostadin has also been a key figure in the development of Bulgarian energy legislation since 2000. He and his team are ranked among the top Bulgarian energy experts in the world’s leading legal directories Chambers & Partners, Legal 500 and IFLR1000.

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"Kostadin Sirleshtov is excellent. He's always available and thinks about our needs and what support he can provide."

Chambers Europe

"Kostadin Sirleshtov is a superb professional, who has extensive expertise in the oil and gas sector, is very client-oriented and has strong connections with the relevant authorities."

Legal 500

Kostadin Sirleshtov is a stellar figure in the sector, with one client highlighting his "in-depth knowledge of the power market both in Bulgaria and South-Eastern Europe."


Relevant experience

  • YGY Industries on the sale of the 229-megawatt St. George greenfield solar plant in Bulgaria's Silistra municipality to Rezolv Energy.
  • Czech Consortium Škoda Transportation and Škoda Vagonka in their successful participation in a public procurement procedure held by Metropoliten Sofia, the metro operator in the Bulgarian capital Sofia. 
  • Vier Gas Transport GmbH on the preparation, application and bid processes for a public procurement procedure held by the Bulgaria-Greece gas interconnector company ICGB AD.
  • Acwa Power/First Reserve and Crescent Capital on the successful legal due diligence and acquisition of the largest PV project in the Balkans to date, with 61 MWp installed capacity, called the Karadzhalovo PV power plant.
  • Enel Green Power on the sale of a 42MW wind park in Bulgaria to the Switzerland-headquartered energy company MET Group.
  • Aksa Energy on the market entry of the client in Bulgaria in wind power projects.
  • Astronergy Solar Development on the acquisition of new greenfield RES projects, including negotiations with sellers, financing and refinancing, CP completion, and post-completion project development activities.
  • Global Biomet on obtaining a licence for a photovoltaic plant in its portfolio.
  • A consortium of major international oil & gas companies on the largest oil & gas exploration project in Bulgarian history, the offshore Black Sea “Han Asparuh” block.
  • Petroceltic (formerly Melrose Resources) on its oil & gas exploration activities in Bulgaria, including recently on the successful negotiations and signing of an extension of the exploration of oil & gas in the Black Sea’s Galata block, new production concession agreements, on negotiations and on-going work related to the intended project for the conversion of a depleted field into a gas storage facility.
  • Toshiba International Europe Limited on the successful completion of its EUR 50m rehabilitation project on Units 5 and 7 of the largest thermal power plant in Bulgaria, Maritsa East 2.
  • ENEL (Italy) on the Belene nuclear power plant, including preparing the feasibility studies and advising the project consultant during the implementation stage.
  • The Bulgarian Nuclear Regulatory Authority on various public procurement and regulatory matters.
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Memberships & Roles

  • Blagoevgrad Bar Association
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Awards & Rankings

  • Top ranked for Energy, Chambers & Partners Europe, 2023
  • Leading individual for Energy and natural resources and Projects and PPP, Legal 500, 2023
  • Market leader for Project Development, IFLR1000, 2023
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  • The Debrief, August 2023, CEE Legal Matters
  • Diversification of the Gas Supply, New Nuclear Projects, and Balancing Capacities for Bulgaria, June 2023
  • Bulgaria: Trends Toward Floating Solar, Agrivoltaics, and Offshore Wind, CEE Legal Matters, May 2023
  • The Debrief, March 2023, CEE Legal Matters
  • CDR, The Belt and Road Initiative, Bulgaria, October 2022
  • Bulgaria: Energy and Infrastructure Attract Investor Attention, September 2022, CEE Legal Matters
  • ESG: Reimagining Energy in CEE, June 2022, CEE Legal Matters
  • CEE Legal Matters Comparative Legal Guide: Oil & Gas 2022
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Lectures list

  • Presenter at the BBSPA Energy Transition Seminar, 3rd edition, 21 June 2023, Sofia, Bulgaria
  • Lecturer at the BBSPA Regional Oil & Gas Conference, Istanbul, 17, November 2022
  • Lecturer at the 7th CEE Nuclear Congress, Prague, 12-13 September 2022
  • Presenter at the BBSPA Energy Transition Seminar, 21 June 2022
  • Presenter at the BBSPA Conference, Prague, April 2022
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  • 2019 – Diploma in Leadership and Management of Law firms, Harvard University, USA
  • 2000 – LLM, Sofia University "St. Kliment Ohridski"
  • 2000 – EU Law and Contemporary English law, Cambridge University, Cambridge
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Bulgaria passes Ordinance offering international trade with guarantees...
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COP28 Update – 7 December 2023
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Race for Leadership: Energy Efficiency and Renewables Fund Seeks New Manager
The Bulgarian Energy Efficiency and Renewable Sources Fund (EERSF) is currently in search of a new manager for a 5-year term, in compliance with local laws. Only legal entities or associations thereof...
Bulgaria to call for 4th tender for offshore Han Tervel Block
On 23 August 2023, the Council of Ministers voted to open another tender for awarding the Han Tervel block, offshore Bulgaria. The licence is for prospecting and exploration of oil and gas for an initial...
Bulgaria extends revenue cap on energy producers and traders until end...
The Bulgarian measures under Council Regulation (EU) 2022/1854 of 6 October 2022 addressing the high energy prices expired at the end of June 2023.Through a proposal by the Council of Ministers of Bulgaria...
Bulgaria's Ministry of Energy proposes establishment of energy communities
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Bulgarian regulator sets new reference prices in expectation for a Contract...
On 30 June 2023, the Energy and Water Regulatory Commission (EWRC) published a Decision regarding the determination of Feed-In Tariffs for electricity produced by renewable energy sources, which updates...
Bulgaria 2053 energy outlook: renewables, nuclear and storage
On 23 January 2023, the Bulgarian Ministry of Energy published its Strategic Vision for Sustainable Development of the Energy Sector of the Republic of Bulgaria, which reflects the national priorities...