The Japan International Cooperation Agency and the Government of Tonga have signed the minutes of their discussions on the installation of a wind power generation system for Tongatapu.
The signing ceremony marked the end of the project's preparatory survey which began last June.
The project aims to diversify Tonga's power supply which still relies on diesel generators.
As well as wind turbines, a stabilisation system for the power grid could also be installed.
The documents will be submitted in March to the Japanese cabinet for final approval and, if given the go ahead, the agency said the wind power project could be completed by 2019.
In 2015, Japan installed a one megawatt solar powered micro-grid in Tonga, two years after introducing a solar powered home system for the outer islands.
It is currently funding the development of the Nuku'alofa domestic wharf with the construction of a new terminal building which began last week.