Samuli Tarkiainen

Partner, Member of the Finnish Bar

I believe that the best results in any project – be it a re-domiciliation of a corporation, the construction of a power plant or an investment into infrastructure assets – can be achieved through business understanding, focusing on the solutions and being pragmatic. In fact, this is true in all situations where we are on board as counsel. And of course, the fundamental core we provide is market-leading legal expertise.

During my practice as an attorney and in-house lawyer, I have gained extensive experience of industrial projects and contracts as well as corporate transactions and restructurings, especially in the energy industry and the financial sector.

It has been very inspiring to provide strategic legal advice on certain key energy and infrastructure projects – green and brownfield, joint ventures, public private partnerships, and consortiums – and on various purchasing, delivery, outsourcing and other contracts. From the field of energy, my experience includes many types of renewable energy technology, such as solar, wind, biomass, biofuels, energy from waste, wave power, geothermal and hydro, as well as conventional power and CHP. I find it rewarding to be part of facilitating change and sustainability in our energy system.

I regularly represent major companies and international investors in public, private, venture capital and private equity transactions and restructurings, with a specific focus on industry, energy, utilities and regulated businesses. I have also been involved in compliance matters and practice in a broad range of business law.

Latest references

We are acting as the joint legal advisor to Oomi Oy and Lumme Energia Oy in a transaction whereby Lumme Energia will merge with Oomi. As from the completion of the merger, the combined entity will be the largest electricity retail and service company in the Finnish market. In 2024, Oomi reported a turnover of EUR 373.9 million and had approximately 110 employees. Lumme Energia’s turnover for the same year was approximately EUR 314.6 million and it had approximately 50 employees. The transaction is primarily driven by the recent developments in the electricity market and the strategic goal to develop competitive products and services. Another key objective is to further enhance the customer experience, which is a shared value between the two companies. As a result of the merger, Lumme Energia’s customers will transfer to Oomi, and Lumme Energia will become one of Oomi’s shareholders. The completion of the transaction is subject to an approval by the Finnish Competition and Consumer Authority.
Case published 29.8.2025
We assisted Oomi Oy in its expansion into the mobile telecommunications market with the launch of Oomi Mobiili, a new MVNO brand. Our work covered the preceding due diligence process as well as structuring and negotiating key partner agreements, laying a solid foundation for Oomi’s entry into the new market. Oomi Mobiili will operate as a virtual mobile network operator, offering customers the option to purchase a mobile subscription together with their electricity contract. The phased launch is set to begin in autumn 2025, with nationwide availability targeted for early 2026. 
Case published 15.8.2025
We advised Nevel Oy in its acquisition of the business of Labio Oy. Lahti Aqua Oy and Salpakierto Oy sold their entire shareholdings in Labio to Nevel, expanding Nevel’s already significant biogas portfolio. The transaction will have no impact on Lahti Aqua’s water utility operations or Salpakierto’s municipal waste management responsibilities. Labio’s operations and customer relationships will continue as before. ‘This partnership is a natural next step for us as we continue investing in sustainable material efficiency and renewable energy solutions. By integrating Labio’s comprehensive offerings and expertise, we can provide customers with a strong platform for material circularity. We are also strengthening our market position as one of Finland’s leading material efficiency solution providers,’ says Ville Koikkalainen, Director of Industrial and Biogas Business at Nevel. Nevel is an energy infrastructure company offering advanced, climate-positive solutions for industry and real estate. It operates more than 130 energy production plants and manages over 40 district heating networks. Nevel’s annual turnover is EUR 150 million, and it employs 190 experts in Finland, Sweden and Estonia.
Case published 16.7.2025
We advised Oomi Solar Oy on the sale of a 250-megawatt solar power project portfolio to Suomen Aurinkovoima Oy. The portfolio consists of ten separate projects, marking a significant development in the Finnish solar energy market and enabling over EUR 100 million in investments. Construction of the first projects is expected to commence as early as 2025, with sites located across various regions of Finland.
Case published 30.5.2025
Castrén & Snellman is acting as the legal advisor to the City of Pori and Pori Energia Oy in the finance arrangement whereby debt facilities in the total amount of EUR 292 million are secured for the purpose of refinancing the existing liabilities and fuelling the future growth of Pori Energia. Pori Energia and its financiers signed a Finnish law governed facilities agreement for this purpose on 13 January 2025. Pori Energia, a multi-utility company, operates in various sectors including district heating, electricity distribution, and electricity generation through CHP and renewable sources. The company also provides wind power services and industrial energy solutions in the Satakunta region where it has c. 60,000 customers.
Case published 6.2.2025
Castrén & Snellman is acting as the legal advisor to the City of Pori in its sale of a 49% stake in Pori Energia to Polhem Infra. Pori Energia, a multi-utility company, operates in various sectors including district heating, electricity distribution, and electricity generation through CHP and renewable sources. The company also provides wind power services and industrial energy solutions in the Satakunta region. This strategic partnership between the City of Pori and Polhem Infra aims to enhance Pori Energia’s financial stability and investment capabilities, enabling the company to further its efforts in the energy transition and continue delivering high-quality energy services to its customers. Polhem Infra, owned by Swedish state pension funds, focuses on investments in critical infrastructure, including renewable electricity generation, energy storage, energy distribution, digital infrastructure, and transport infrastructure. The transaction values Pori Energia at EUR 905 million. 
Case published 31.1.2025
We are advising Oomi Oy in a business transaction whereby KSS Energia Oy’s consumer and business customers in the retail sale of electricity will be transferred to Oomi. The transfer is scheduled to take place in March 2025. The arrangement requires approval from the Finnish Competition and Consumer Authority. Oomi Oy is one of the largest energy service companies and electricity sellers in Finland. The arrangement is a result of the recent development of the electricity market and Oomi’s strategy, which aims to offer customers a seamless and improved digital customer experience.
Case published 20.12.2024
We acted as the lead counsel to Fortum in a cross-border transaction in which Fortum sold its recycling and waste business. The business was sold to thematic impact investing firm Summa Equity through its portfolio company NG Group. The debt-free purchase price is approximately EUR 800 million.  Fortum’s recycling and waste business to be sold comprises municipal and industrial waste management and end-to-end plastics, metals, ash, slag and hazardous waste treatment and recycling services. These businesses are located in Finland, Sweden, Denmark and Norway and currently employ approximately 900 employees.
Case published 18.7.2024