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Portrait of Kostadin Sirleshtov

Kostadin Sirleshtov

Managing Partner
CEE Head of Energy & Climate Change

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

Kostadin Sirleshtov is Managing Partner at CMS Sofia and Head of Energy & Climate Change for CEE.

His particular area of expertise is in conventional, nuclear, renewables, oil & gas, infrastructure, projects, PPP, public procurement, underground resources. He has worked as the Chief of the Minister’s cabinet for the Ministry of Energy and Energy Resources. 

Kostadin has vast experience in the conventional power and electricity sector. He has represented clients, including renewables organisations, in negotiations with the Bulgarian Government, National Electricity Company and the Electricity Transmission System Operator. He has also advised major international oil & gas prospecting and exploration companies in Bulgaria on various onshore and offshore projects. In addition, he is particularly focused on advising renewables companies (in relation to wind, hydro, solar and biomass projects) on the development, operation and/or sale of their projects in Bulgaria, including on litigation matters.

Kostadin is ranked as one of the top Bulgarian energy experts in the world's leading legal directories Chambers & Partners and Legal 500.

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"Top-rated energy partner Kostadin Sirleshtov leads the team, and is praised by interviewees as a "distinguished, pleasant and upbeat" lawyer with "huge knowledge and understanding of the sector." "


Relevant experience

  • A consortium of major international oil & gas companies on the largest oil & gas exploration project in Bulgarian history – offshore Black Sea “Han Asparuh” block. The work included authorisations grant assistance, environmental regulations and other regulatory assistance, assistance in the preparation and conduct of the calls for tender for the procurement of the operational contracts, public procurement assistance, representation before governmental authorities etc.
  • Petroceltic (formerly Melrose Resources) on their 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, negotiations and signing of new production concession agreements, on-going work related to the intended project for the conversion of a depleted field into a gas storage facility. Petroceltic is Bulgaria’s biggest British investor and since 2001 has discovered four deposits of natural gas and produced natural gas in excess of 3 billion m3.
  • Toshiba International Europe Limited on the successful completion of their EUR 50m project for rehabilitation on Units 5 and 7 of the largest Thermal power plant in Bulgaria Maritsa East 2. We advised on all legal and strategic aspects of this largest deal in the electricity sector in Bulgaria to date, including on first stage of the project for replacement of the turbine at Unit 2 of TPP Maritsa East 2 estimated at EUR 25m.
  • ENEL (Italy) on the Belene nuclear power plant, undertaking full legal due diligence of the Belene nuclear project. Members of our team were involved in preparing the feasibility studies and advising the project consultant during the implementation stage.
  • Foster & Partners on the project design agreement of the new Passenger terminals for Varna and Burgas Airports. The project involved the preparation of the offer and the respective documents, representation during the negotiation phase and revision of the design contract.
  • SDN Company and Korea Development Bank (Korea) on the legal due diligence and acquisition of 5 solar projects in Bulgaria with installed capacity of 58 MW and the establishment of a local subsidiary. The work included: corporate and regulatory advice; legal due diligence; negotiations; assistance with implementation, the successful financing of three projects worth EUR 180m from Korea Development Bank and Unicredit Bulbank.
  • Iberdrola Renovables SA (Spain) on the acquisition of a 74 MW wind farm project in Northern Bulgaria. The work included full legal due diligence, preparation of the transactional documents, completion of the security package and post-closing assistance. This project, worth over EUR 150m, is among the biggest wind farm acquisition projects in Bulgaria. Upon acquisition, we assisted the client with the licensing of the project with the Bulgarian State Energy and Water Regulatory Commission and in the negotiations with the Bulgarian National Electricity for the signing of the Final grid connection agreement.
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  • Regular publications in the International Comparative Legal Guides to Oil & Gas Regulation, Mining Law, Environmental and Climate Change Law, Public Procurement.
  • Chapter on Energy in Bulgaria in the 3rd edition of Energy Global Legal Insights. 
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Lectures list

  • 5th Regional Energy Conference (October 28-29, 2014, Sofia)
  • Gas Storage and Transmissions (June, 17-18th June 2015, London)
  • The Eurasian Natural Gas Infrastructure Conference (June 9-10, 2015, Istanbul)
  • Energy from Waste Conference (October 2014, London)
  • Shale Gas Environmental Summit (October 2014, London) 
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  • 2000 – LLM, Sofia University St. Kliment Ohridski, Sofia
  • 2000 – EU Law and Contemporary English law, Cambridge University, Cambridge
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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
A bill amending and enhancing the Energy Act, proposed by the Bulgarian Ministry of Energy (MoE), has entered the public discussion stage. The MoE published their proposed draft amendments to the le­gis­la­tion...
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...
Bulgaria to develop electricity storage to enhance development of re­new­ables...
Early 2023 the Bulgarian parliament introduced legislative amendments to enhance the development of the renewables sector. By means of amendments and sup­ple­ment­a­tions in the Energy Act (EA), three major...
Bulgaria to increase renewable energy deployment in 2023
In December 2022, the Bulgarian Ministry of Energy completed public con­sulta­tions for legislation that amends the Renewable Energy Act and changes the Energy Act, Energy Efficiency Act and the Pro­tec­tion...
Bulgaria implements EU regulation on intervention to address high energy...
Bulgaria has implemented Council Regulation (EU) 2022/1854 of 6 October 2022 on emergency intervention to address high energy prices through amendments to &8 and &9 of the Law for the 2023 Bulgarian state...
ESG and the energy sector
This article first appeared in the Future of Emerging Europe: Sus­tain­ab­il­ity Report 2022.  A copy of the full report is also available to access here.De­vel­op­ments in ESG issues in emerging Europe’s en­ergy sector continue apace. Energy gen­er­a­tion com­pan­ies, governments, local authorities and con­sumers are all affected by the drive towards a future that is less reliant on fossil fuels.
ESG in emerging Europe hub
The focus on ESG (en­vir­on­ment­al, social and governance) in emerging Europe has increased notably following the EU taxonomy coming into force at the beginning of 2022. EU-driven initiatives, including policies coming out of the European Green Deal (EGD) to fight climate change have started affecting the industry, and with tightening regulation as well as reporting and compliance obligations, there is certainly more to come. 
Bulgaria to develop 62 GW capacity of offshore wind potential
The Energy from Renewable Sources at Territorial Waters of Bulgaria Bill (the “Bill”) governs the public relations regarding the power production from offshore wind farms in the sea waters of Republic...
Reimagining Energy in CEE
CEE Legal Matters spoke with CMS Partners Agnieszka Skorupinska, Kostadin Sirleshtov, and Varinia Radu about the impact of ESG on the energy sector in CEE. Growing Pains “The energy sector is very much...