Graduate in economic & law, University Freiburg & University Göttingen, Germany, 1984. Juris Doctor, University Göttingen, 1991.
He then went on to pursue doctoral studies in Boston, US, but returned to Germany to finish in 1991, earning a Doctor of Jurisprudence degree. After that he became a research assistant at Gottingen University. Teyssen’s first career role was as a law clerk at the State Superior Court in Celle, Germany.
He stayed in that position until he joined PreussenElektra in Hanover in 1989. In 1991, after finishing his doctorate, he was promoted by PreussenElektra to head of energy and corporate law. In 1994, he earned another promotion, this time as head of legal affairs after his talent as a litigator was spotted by his superiors.
One year later, he was named chairman of the board of management at Avacon, based in Helmstedt. In 2001, leveraging his energy and technology experience, and proven management abilities, he moved to E.ON Energies AG and two years later became chairman of its management board. In 2004, he was appointed to the board of Fortum Espoo Oyj (formerly known as EON Finland Oyj) and in 2005, he was promoted to chief operating officer and deputy chairman of the board for E.ON Ruhrgas AG and E.ON Energy Trading AG. By 2008, he became COO for the entire group and was later appointed vice chairman and deputy CEO. In May 2010, Teyssen became CEO of E.ON Group.
His tenure has been marked by decisions concerning Germany’s switch to renewable energy, which he cited as a huge opportunity. In January 2012, he spoke out against the European Union’s Emissions Trading System and in 2013, he questioned the profitability of gas-fired plants. In addition to his role at E.ON, Teyssen sits on the supervisory boards of Deutsche Bank AG and Salzgitter AG.
In 1998, Teyssen joined the Hanover-based power company Hastra in his first executive position as member of the board.