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Portrait of Kostadin Sirleshtov

Kostadin Sirleshtov

Managing Partner
CEE Head of Energy & Climate Change

CMS Sofia
Landmark Centre
14 Tzar Osvoboditel Blvd
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 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 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...
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...
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...
Bul­gari­a's plans to in­crease con­ces­sion fees un­der­mines po­ten­tial gas pro­duc­tion
After sev­er­al years of de­bate, the Min­istry of En­ergy has draf­ted a new or­din­ance on the meth­od­o­logy for con­ces­sion pay­ments for un­der­ground re­sources.  The con­ces­sion pay­ment is cal­cu­lated as a per­cent­age...
Bul­garia price hike in re­new­able en­ergy spells 20% short­fall for reg­u­lated...
Bul­gari­a's En­ergy and Wa­ter Reg­u­lat­or Com­mis­sion (EWRC) an­nounced on 1 Janu­ary 2022 that re­new­able en­ergy pro­du­cers in Bul­garia will see their es­tim­ated mar­ket prices rise from BGN 119 per MWh to BGN...
Bul­gari­an En­ergy Sec­tor (2022-2025) 
What are the im­me­di­ate and the long-term goals of the new Bul­gari­an Gov­ern­ment in the en­ergy sec­tor  Fol­low­ing three Gen­er­al elec­tions (held in April, Ju­ly and Novem­ber 2021), on 13 Decem­ber 2021 the...
Hy­dro­gen law, reg­u­la­tions & strategy in Bul­garia
1. Cur­rent State of Hy­dro­gen Pro­jects in Bul­garia Hy­dro­gen pro­jects are in the mid to long-term pipeline of the Bul­gari­an en­ergy policy. Hy­dro­gen has been re­cog­nised as an area to be fur­ther de­veloped...