Much rain, a steep drop and nearness to Bergen meant that the power-making potential of the Samnanger water system was exploited early. Samnanger was thus one of the first power-producing municipalities in western Norway. With its subsequent expansion and new power stations, about 400 gigawatts of electricity per hour were produced on average each year. This is enough to meet the energy needs of 25,000 households.
In 1923 Bergenshalvøens Kommunale Kraftselskap (BKK) expropriated large areas for power plants and development of hydropower started soon afterwards. Dale power station with the two first aggregates, each of 14 MW was put into operation on 17 November 1927. In the supply reservoir in Storefossen 5152 cubic metres of concrete were cast, and a modern and well-equipped power station was built.
Water discharge at the outlet of the Ekso into Eidsfjord was halved after the big hydropower development in the mountainous area between Modalen and Eksingedalen and further southward toward Evanger in the 1960s, 70s and 80s. In an attempt to amend the changed environmental conditions in the waterway the developer built 35 small dams in the river.