Indonesia has the world’s largest potential geothermal resources due to its unique location near the ring of fire. The development of the geothermal power projects as one of the strategic and environmentally friendly energy sources has become the priority of the Government of Indonesia to promote renewable energy from geothermal resources.

Apart from tapping the rich geothermal resources, geothermal power projects are in line with Government’s objective in which Sarulla Project can contribute 330 MW as part of the Government’s plan in providing 35,000 MW electricity nationwide.

Sarulla Operations Ltd (SOL) is sponsored by a consortium of Medco, Itochu, Kyushu, Inpex and Ormat. The total investment of the project is USD 1.7 billion. The second amendment of the ESC (Energy Sales Contract) and JOC (Joint Operation Contract) between SOL, PLN and PGE was signed on April 4 2013. SOL has built the world's largest Geothermal Power Plant in a single contract, with a capacity of 3 x 110 MW to contribute the electricity needs in North Sumatra.

The Sarulla project is located in Pahae Julu and Pahae Jae Districts, North Tapanuli Regency, North Sumatra Province. The first unit was operated commercially in March 2017, the second unit was operated in October 2017 and the third unit was started to operate in May 2018.

The geothermal power plants are fueled by steam and brine from production and injection facilities at Silangkitang and Namora-I-Langit reservoirs. The power plants utilize geothermal combined cycle units which are more efficient than conventional flash type geothermal power plants. The plants capture the steam and brine from the wells and produce energy throughout the day which are intended for base load operation. The condensate steam and the brine water are re-injected to underground via wells to maintain sustainable geothermal resources.