The Hekni run-of-the-river power plant is located just below the town of Rysstad in Bygland municipality, Aust-Agder county.
This power plant receives its water from the Otra watercourse and utilises a 38.5-metre waterfall from a dam at Tjurmo. The total output is 56 MW. The power plant has two Kaplan turbines and was commissioned in 1995.
Owners: Skagerak Kraft AS 33.33%, Agder Energi AS 66.67%.