Aerial Nuku Alofa and Tongatapu Island © iStock; Aerial Nuku Alofa and Tongatapu Island © iStock;

Tonga energy roadmap, Kingdom of Tonga

Shaping Tonga’s energy future

The opportunity to drive the redesign of an entire country’s energy network doesn’t come along every day, but Arup is doing that now in the Kingdom of Tonga, the remote South Pacific island nation, 2400kms from New Zealand.

At present, almost 80% of Tonga’s energy generation is from diesel. Fuel accounts for 25% of all imports by value and 10% of GDP. Arup is working on a transformational project to reduce Tonga’s vulnerability to oil price volatility and improve its economic and environmental position.

We are working with the country’s electricity provider, Tonga Power Limited (TPL), to ensure an orderly transition to greater levels of renewable energy sources – wind, solar and Battery Energy Storage Solutions (BESS).

It is a tough challenge due to Tonga’s small size, geography, weather and climate. We have been developing an Energy Roadmap which will enable it to achieve 58% renewable energy generation by 2020, with an increasing deployment to the maximum possible by 2030. This is significantly more than previously thought feasible.

Project Summary


260km2 land size of Tongatapu

58%renewable energy by 2020 through wind, solar and battery storage

75,000people on Tongatapu

A unique opportunity

Tonga had a ten-year Renewal Energy Roadmap but with three years left to meet their 2020 target of 50% renewable energy, it asked Arup to assist.

Beyond technical assistance, and by taking a ‘total design’ approach, we determined that 58% renewables were achievable within three years and in fact cheaper than aiming for 50%. We also advised on a 91% figure for 2030 to ensure maximum renewable energy efficiency, and to enable grid reliability and stability.


A challenge or two…

For small island nations like Tonga, the challenge is considerable. With a land mass of only 260km² for the main island, Tongatapu, cloud cover is problematic as well as the trade winds, which blow only in the morning and early evening, leaving at least 12 hours downtime to consider.

Detailed analysis has determined the optimal energy mix while providing indicative costs for the design, procurement and installation of the new facilities.

Our roadmap includes plans to create a hybrid solar, wind and BESS microgrid on Tongatapu. However, the annual cyclones present a problem with wind generation, limiting the size of wind turbines. For reliability, some portion of diesel generation will potentially need to remain as back-up.

Matatoa Solar Farm commissioning ceremony © Tonga Power Limited Matatoa Solar Farm commissioning ceremony © Tonga Power Limited
His Majesty King Tupou VI, Hon. Poasi Tei (Minister of Public Enterprises), Carl Sanft (Chairman of the Combined Utility Board) at the Matatoa Solar Farm commissioning ceremony. The solar plant was the first large scale project in the development of renewable energy in Tonga. © Tonga Power Limited

A game-changer for the people of Tonga

For Tonga, low-cost, green, reliable energy is a game-changer.

The economic impact of achieving the projected outcomes extends beyond reducing imported fuel costs. A reliable and sustainable energy source can enable Tonga to make new plans for the economy — improve agricultural productivity, develop the tourism industry and invest in upskilling its people.

We continue to work with TPL, helping it to achieve its targets.


This is a one-in-a-million opportunity to help shape the energy future of a country, to make an enduring difference not only to people’s lives, but to the economy and environment too. ”

Merrill Lee Merrill Lee Energy Advisory Leader