Following the 2016 elections in Germany's important state of Baden-Württemberg, he was again part of the negotiations on a coalition government, this time of the CDU and the Green Party under Minister-President Winfried Kretschmann.

[3] With the formation of the fourth Grand Coalition under Merkel in 2018, it was announced that Bareiß would move to the position of Parliamentary State Secretary at the Federal Ministry of Economic Affairs and Energy under Minister Peter Altmaier.

[7] Ahead of the Christian Democrats' leadership election in 2018, Bareiß publicly endorsed Friedrich Merz to succeed Angela Merkel as the party's chair.

[9] In 2010, Bareiß worked to limit the growth in solar-panel installations in Germany as he saw the rising costs to consumers undermine the acceptance of alternative energy.

In a letter to then-Environment Minister Norbert Röttgen, he demanded that the government cut the guaranteed gratuity per kilowatt hour for newly installed solar panels by an extra amount.

According to reports in several German media outlets, during the conversation Bareiß "insisted in the telephone call that ventilators be delivered first to Baku and that this was due to the good economic relations between Germany and the Caucasus Republic.

"[34][35] The Federal Ministry of Economics also stated that Thomas Bareiß had "at no time asked a representative of Löwenstein Medical to give priority to the delivery of ventilators to Azerbaijan.