Nam Theun 1 Dam Hydropower Info by Hobo Maps - Go to Hydropower Projects Page - - Home
The Nam Theun 1 project is located on the Nam Kading (river) about 33 km upstream from where the Nam Kading joins the Mekong near Pak Kading town on the border between Bolikhamxai and Khammouane Provinces. The project is near Phon Charoen Village in Pak Kading District, Bolikhamxay Province of Lao PDR.
Nam Theun is pronounced as "Nam Tune".
Nam Theun 1 location is shown in satellite image below at coordinates 18°21'25.2"N 104°08'52.8"E (18.357, 104.148):
The project is owned and developed by Nam Theun 1 Power Company, a joint venture in the beginning of Phonesack Group (PSG 32%), Chaleun Sekong Energy Company (CSE 28%), Electricity Generating Public Company of Thailand (EGCO 25%), and Electricite Du Laos (EDL GEN 15%). In Oct. 2025 EDL Gen sold all of its 15% interest to Chaleun Sekong Energy Company, increasing its share to 43%. Other transactions occurred later and as of February 2026, Charoen Sekong Power Limited (CSE) holds a majority share of 75% while EGCO retains its original 25% share.
Project cost is estimated at US$ 1,335 million with receipt of foreign funding support accounting for 70% of the total capital, comprising: 1) Bangkok Bank–39%, 2) Siam Commercial Bank (SCB)–39%, 3) Export-Import Bank of Thailand (EXIM Thailand)–11%, 4) TISCO Bank–11%, as well as 30% of the project capital contributed by other shareholders.
Nam Theun 1 hydropower project images below:
The project will operate as Build-Operate-Transfer (BOT) type with a concession period of 27 years.
The project is designed for hydro-peaking with 80% of 650 MW output (520 MW) going to Electricity Generating Authority of Thailand (EGAT) and 20% (130 MW) to Electricite du Laos (EDL). The 650 MW project can generate up to 2,562 GWh output per year.
The project has a 27-year power purchase agreement with EGAT.
Construction of the project started in 2017, reservoir impounding began in June 2021 and full operation and commissioning was in August 2022.
Nam Theun 1 reservoir image below:
The main dam structure is a 177-meter-high curved-gravity Rolled Compressed Concrete (RCC) dam with a gated crest spillway. Elevation at top of dam is 272.9 meters above sea level.
The powerhouse is located on the left bank of the river 450 meters downstream from the dam structure.
The powerhouse has 3 vertical axis Francis turbine-generator units (2 x 260 MW each for 520 MW combined output exported and sold to Electricity Generating Authority of Thailand (EGAT) and 1 x 130 MW unit with output sold to Electricity du Laos (EDL) for domestic consumption. All three units combined total 650 MW and are capable of generating an average annual electricity output of approximately 2,562 GWh.
Facebook video created July 2022 during commissioning exercises HERE .
October 1, 2025 see video of excess water releases
Nam Theun 1 site images below:
A diversion tunnel located on the right bank allows dry season floods of the Nam Kading to pass safely. Allowance is also made for safe overflow during the rainy season of the main dam and the two cofferdams.
An intake structure located above the dam takes water down a headrace tunnel to the powerhouse. The bifurcated headrace tunnel is a reinforced concrete lining type with 565 meters length for the EDL Shaft and 544 meters length for the EGAT Shaft.
Full reservoir capacity is about 3 billion cubic meters with 2 billion of that as active storage. Normal reservoir water surface level is 292 meters above mean sea level. The catchment area covers 13,856 square km.
The Nam Theun 1 hydroelectric power plant operates with a head of about 140 meters.
The project involves a diversion channel, a headrace tunnel connected to a steel penstock, a spillway and a tailrace channel.
Nam Theun 1 intake image below:
Nam Theun 1 turbine images below:
Nam Theun 1 plant images below.
Nam Theun 1 controls images below:
Nam Theun 1 Hydropower Project Details below:
The Nam Theun 1 reservoir gets its water from the large and wet 14,000 square km Nam Theun-Nam Kading catchment basin.
The unrelated and upriver Nam Theun 2 HPP diverts much of the runoff from the Nakai Plateau away from the Nam Theun river and instead channels the flows south into the Xebangfai river which decreases the water flowing into Theun-Hinboun HPP and Nam Theun 1 HPP as seen in chart below.
Contractors of the Nam Theun 1 hydropower project
Italian-based Cooperativa Muratori e Cementisti (CMC) together with Italian-Thai Development Public Company and Vietnamese state-owned Song Da Corporation were contracted for civil and hydro-mechanical works of the project.
Song Da Corporation’s work included blasting, excavation and transportation of soil and rock as well as construction of the crushing and batching plant and the cofferdams for the project.
Italian-based ATB Riva Calzoni supplied the penstocks, bottom outlet and other hydro-mechanical equipment.
China’s state-owned Sinohydro Bureau 3 was engaged in civil works for the project.
Vienna-based Andritz Hydro provided the design, manufacture and supply of electromechanical equipment. This includes three vertical Francis turbines with a total output of around 650 megawatts, generators, governors, automation system, main transformer, switchgears, power and control cables, fire protection system, 500kV Gas Insulated Switchgear), the main inlet valve, mechanical auxiliaries, installation supervision and commissioning.
Poyry (now Afry) was engaged as the owner’s engineer and was responsible for the coordination at design level between contractors and for issuing construction drawings to the main civil contractor.
Thai-based Right Tunneling handled the underground excavation and concrete lining works for the project.
Nam Theun 1 images below during tests for commissioning July 2022
Nam Theun 1 construction in progress images below:
Project history below from CS Energy website Nov. 2021:
Project History below from Chaleun Sekong Energy Co., Ltd Facebook posting Feb. 2026:
The project commenced its feasibility study on 19 February 2014, conducted by Pöyry consulting company. The study examined several alternative development options, including a run-of-river scheme and a reservoir-type scheme. Based on the study results, the reservoir-type option was selected as the final project configuration on 8 August 2014.
Construction of the Nam Theun 1 Hydropower Project commenced in 2017, with the civil works undertaken by a joint venture consisting of Italian-Thai Development Public Company Limited (ITD), CMC (Italy), and Song Da Corporation as the main contractors. Subsequently, in order to ensure that the project could be completed in accordance with the conditions stipulated in the Power Purchase Agreement (PPA), the construction contractor was changed to Sinohydro, while the electromechanical equipment installation was undertaken by Andritz Hydro.
The Nam Theun 1 main spillway has six radial gates 20.3 meters wide by 17.3 meters high with ski-jump style landings into a plunge pool. These may have been the largest radial gates installed in Laos at the time. Radial gates & spillway design image below.
Nam Theun 1 transformer and switchyard images below:
The electrical transmission infrastructure at the project site includes transformers, low and medium-voltage switchgears and a 500 kV gas-insulated substation.
For EDL offtake, a 115 kV transmission line takes power 9 km to the Paksan-Khonsong substation. For EGAT offtake, a 500 kV transmission line takes power 154 km to Nabong substation near Vientiane for re-transmission to Thailand as seen in map below. See enlarged version HERE
Name Confusion - Why not Nam Kading HPP?
Nam Theun 1 (NT1) hydropower project has a confusing name since the project is neither on nor near the Nam Theun river. The Nam Theun 1 project is actually located on the Nam Kading river near Pak Kading town on the Mekong. Nam Kading river at some time in the past may have been called the Nam Theun since it is basically the same water course.
Nam Theun 1 hydropower project also has no connection with the Nam Theun 2 (NT2) hydropower project either geographically or by ownership. NT2 was actually created first and has been operating since 2010. Water from the Nam Theun river does flow into the Nakai reservoir that powers the NT2 project but outflows from the NT2 powerhouse now are diverted into a different drainage basin and no longer flow into the Nam Theun river that ends up as a tributary of the Nam Kading.
Massive size and 236 tons weight of 500 kV transformer for Nam Theun 1 required special transport of 1,100 km from Thailand to Laos across the Mekong as seen in images below:
See our Map of area's basins and drainage .
Map below shows Nam Theun 1 Dam Hydropower project in upper left near Pak Kading:
