Athens · Greece & Europe
MAVSIG invests in battery energy storage systems and prime real estate — pairing the speed of the energy transition with the permanence of real assets.
01 — About
MAVSIG is an Athens-based investment company operating at the intersection of the energy transition and real assets.
We develop and operate battery energy storage systems that strengthen the grid — and we invest in real estate that holds its value across cycles. Both are driven by the same discipline: long-term thinking, careful underwriting, and hands-on ownership.
Founded by two partners with complementary backgrounds in energy and investment, MAVSIG moves with the agility of a private firm and the rigor of an institution.
02 — Energy Storage
As renewables grow, the grid needs flexibility. Battery Energy Storage Systems (BESS) absorb energy when it is abundant and release it when it is needed most.
03 — Investments
ENERGY
Utility-scale storage assets across Greece and Europe, developed from the ground up and held for the long term.
REAL ASSETS
Prime residential and commercial properties in established locations, acquired with discipline and managed directly.
04 — Leadership
Co-Founder & Managing Partner
Vasileios Mavrogiannis is a senior business executive and entrepreneur with more than 30 years of international experience across the energy, finance, investment, healthcare, shipping, and consulting sectors. Throughout his career, he has founded, managed, and advised numerous companies and investment ventures, developing extensive expertise in business development, strategic planning, corporate finance, investor relations, capital raising, and business growth. His ability to identify opportunities, build strategic partnerships, and drive sustainable value creation has contributed to the success of a wide range of projects and organizations across both domestic and international markets.
He has held executive leadership positions including CEO of MAX ENERGY S.A., Founder and CFO of Cosmos Health Inc. (NASDAQ: COSM), and Founder and Director of several international investment and environmental ventures. Recognized for his strong communication, networking, and leadership capabilities, he has successfully built long-term relationships with investors, clients, financial institutions, and key stakeholders while leading complex business initiatives, financing transactions, public market activities, and growth strategies. His multidisciplinary experience and extensive business network continue to support the development and expansion of innovative ventures across multiple industries.
Co-Founder & Managing Partner
Lefteris Sigalas is the Chief Executive Officer of OMNIPHOS S.A. and a Civil Engineer with more than 18 years of experience in the renewable energy sector. Building on the legacy of S. SIGALAS S.A., a prominent engineering and construction company with a strong presence in both the Greek and international markets, he has played a leading role in the development, financing, and implementation of energy and infrastructure projects across Greece and Southeast Europe. His expertise spans project development, strategic planning, business growth, investment structuring, engineering management, and the successful delivery of complex energy and infrastructure projects.
Today, his primary focus is on Battery Energy Storage Systems (BESS), photovoltaic power plants, hybrid energy solutions, and advanced energy infrastructure. Through OMNIPHOS, he works closely with investors, utilities, technology providers, and industrial clients to develop innovative and financially sustainable projects that support the energy transition, enhance grid resilience, and create long-term value. Combining engineering expertise with strong business acumen, he has successfully led multidisciplinary teams and established strategic partnerships that drive growth and innovation in the energy sector.
05 — Contact
Whether you are an investor, a landowner, or a partner — we'd like to hear from you.