In 1985 the Japan International Co-operation Agency (JICA); while preparing a Master plan of the Koshi Basin Water Resources Development, had identified a ‘TA-6’ project close to the existing project site of the Upper Tamakoshi Hydroelectric Project. During a study of the Himalayan region in 1999, an Austrian, Mr. Christian Ulhar carried out pre-feasibility studies and concluded that the project would have an installed capacity of 120 MW.

Because of the competitively low project cost and its overall attractiveness, NEA conducted a first stage detailed feasibility study in 2001 mobilizing their own physical, financial and human resources. This study showed that the new feature of the project when installed would have a capacity of 250 MW and an annual average energy generation of 1570 GWh, at a cost of US$ 1100 per KW. During the study, they completed a detailed engineering design of a 28.5 km long access road and seven different bridges. The study was completed in 2003.

With financial and environmental attractiveness of the project, it was recommended for the second phase of the Detailed Feasibility study, as per international standards. Accordingly, with financial assistance from the Government of Norway, the Norwegian consultant Norconsult AS completed a Bankable Detailed Design Feasibility Study in May 2005. This study presents the installed capacity of the project at 309 MW, with an annual average generation of 1737 GWh of energy.