Hammeren Hydroelectric Power Station (Norwegian: Hammeren kraftstasjon) is a hydroelectricpower station located in Oslo, Norway. It is the only power station in Oslo, and among the oldest power stations still running in Norway. It has a total installed capacity of 5 MW, and an annual production of 16 GWh. The powerstation utilises the waterfalls from Skjærsjøen to Maridalsvannet, with a total height of 105 m. It was established in 1900 by the company Christiania Elektricitetsværk, originally with 4 generator units, and increased to six units in 1901. In 1927 the six generators were replaced by a single 5.6 MW unit.