Ownership: 100 %
Production: 1016 GWh
Power: 180 MW

Mår power plant uses water from watercourses in Tinn Municipality in Telemark County and has a catchment area totalling 770 square kilometres with a mean annual inflow of 560 million cubic metres. The development of the power plant was planned and initiated during World War II, but it was first commissioned in 1948.

The height of fall from the inlet in Lower Grottetjørn Lake is 820 metres. The staircase up through the 1250-metre-long penstock shaft inside the mountain has 3875 steps, making it one of the world's longest wooden staircases.

The power plant has five generating units equipped with Pelton turbines.

The regulated water area for Mår power plant is in the Skien River system and includes the reservoirs Mårvatn, Kallhovd, Gøyst, Strengen and Grotte. These have a combined holding capacity of about 580 million cubic metres of water, sufficient for the production of about 1 TWh of power.

Mår dam is one of the few dams in Norway made of natural stone.