Supporting renewable energy developments in Tonga

Client: Asian Development Bank
Location: Tonga
Date: 2017 - ongoing

Assessing the feasibility of renewable energy developments in Tonga and supporting their construction 


Tonga comprises more than 170 South Pacific islands, many of which are uninhabited. Like most island nations in the Pacific, it is facing the large and looming threats of climate change, including rising sea levels and more frequent and more intense storms. To meet its clean energy goals and mitigate climate risk, Tonga is aiming to be powered by 70% renewable energy by 2030, reducing its heavy reliance on imported diesel.

Entura was engaged by the Asian Development Bank (ADB) to assess feasibility and provide ongoing support during construction for the Tonga Renewable Energy Project (TREP). The TREP is funded by ADB, Green Climate Fund and the Department of Foreign Affairs and Trade, and has been established to provide storage and renewable generation on 8 islands, supporting Tonga’s energy transition to achieve greater climate resilience and environmental sustainability.


The TREP supports installation of more than 10 MW of new private investment in renewable generation on Tongatapu, providing storage and grid stability without which these investments could not proceed. The TREP will also provide new storage and renewable generation on 7 outer islands, with 5 new mini-grids for islands currently without a power station or reliable power supply. This represents a substantial change for local communities who will for the first time have access to a reliable 24/7 power supply.

Entura undertook technical, financial and economic feasibility assessments and due diligence on each of these projects, supporting Tonga’s applications for project finance. We also supported Tonga through the procurement of these projects, with the final tender closing in 2019.

After procurement, Entura has been engaged by Tonga Power Limited to carry out review of the construction contractor’s design development, procurement, and project management plans, and monitored compliance with project safeguards requirements.

Entura has worked closely with the local utilities and the project management unit to develop a COVID-19 Response Plan to manage risks and expedite tasks where possible. This plan, along with close contractor engagement, has been used to assist in managing challenges during countrywide shutdowns, enabling equipment orders to progress and construction on Tongatapu to begin in July 2020. However, due to international travel restrictions and logistics challenges, aspects of commissioning and completion have been rescheduled for early 2021.

With travel to the country on hold, Entura has adapted to the remote working conditions by facilitating aspects such as detailed design reviews, remote witnessing of factory acceptance testing for key equipment, guiding community engagement and safeguards monitoring on the ground. Entura’s team also includes a local Tongan engineer, providing construction supervision for the initial civil aspects of the works and presence on site.

Our involvement in the project will continue through construction of the various TREP components, with Entura poised to mobilise to site for commissioning of battery systems on Tongatapu and supervision of the outer islands subprojects.

Services provided

  • technical, financial and economic feasibility studies
  • technical due diligence
  • community engagement 
  • procurement and contract negotiation
  • design review
  • remote factory acceptance testing


Once completed, the TREP will enable greater access to modern, reliable energy services for around 104,000 people in Tonga. It will also result in greater energy security and affordability by removing the reliance on imported diesel.

Entura’s engagement with the renewable energy projects will support Tonga’s journey towards stronger climate resilience and environmental sustainability. The TREP is a large step towards achieving Tonga’s goal of 70% renewables by 2030.