230 kV Submarine Cables Connect Ko Samui to a Sustainable Future of Energy
19 December 2025Ko Samui in Surat Thani Province is a land of “white sand, clear sea, beautiful reefs, and delicious coconuts.” It is a tropical paradise with natural beauty and a popular destination for travelers around the world. The government is pushing forward to establish Ko Samui as a tourism hub of the Gulf of Thailand, aiming to elevate its tourism status to rank among the world’s top 10 destinations. This means that the infrastructure of Ko Samui must be comprehensively developed, with a special focus on electric power.
Ko Smui’s Power Shortages and Outages
Ko Samui does not have its own power plant but mainly relies on electricity transmitted through submarine cables. The electricity is supplied from Khanom Substation in Nakhon Si Thammarat Province, operated by the Electricity Generating Authority of Thailand (EGAT), through the submarine cable system of the Provincial Electricity Authority (PEA). The system comprises four circuits: two 115 kV circuits and two 33 kV circuits, with a total electricity supply capacity of 174 MW. However, this submarine cable system is aging and frequently malfunctions. As a result, it cannot supply electricity at its full capacity. When the electricity is inadequate, outages frequently occur, especially between April and May, which is the high season of Ko Samui. The power outages in Ko Samui are not new; they are longstanding issues that are intensifying as the tourism business expands continuously. Rolling blackouts and the use of mobile generators are only temporary measures. Establishing a sustainable electricity system requires investment in new submarine cables. This will not only solve electricity crisis but also build confidence among investors and tourists that the island deserves to be a global destination.
Submarine Cable Development to Meet Rising Electricity Demand
The Cabinet approved the Submarine Cable Development Project for Ko Samui District to Enhance System Security (SPSS) on February 28, 2023. The project is one of EGAT’s key development projects included in the draft Power Development Plan B.E. 2567-2580 (PDP 2024) to solve power system instability in the southern islands, namely Ko Samui, Ko Pha-ngan, and Ko Tao in Surat Thani Province, while accommodating the rising electricity demand. The project comprises the construction of two 230 kV submarine cable circuits from Khanom Substation to Ko Samui Substation (new substation) with a total length of 50 km, expansion of Khanom Substation to accommodate 230 kV underground cables, the construction of Ko Samui Substation (new substation), and the installation of two sets of 230/115 kV transformers rated at 300 MVA. When the project completes, it will enhance the capacity of electricity transmission to Ko Samui and nearby islands by 200 MW per circuit, totaling 400 MW. This enables it to meet electricity demand up to four times higher than the current capacity.
Modern, Eco-friendly Cable System
The design of the submarine cable system takes the system stability and environmental care into consideration, starting from the route selection which avoids coral reefs, seagrass beds, shipping lanes, and port areas to ensure safety and maintain the balance of the marine ecosystem. The submarine cable installation utilizes water jetting technology to create a groove where the cable will be laid and buried in the seabed sand at a depth of around 3-5 meters. The groove size is only slightly larger than the cable itself to minimize impact on coral reefs and marine life. The jetted groove restores naturally within 10 seconds. The slit curtains are used during the jetting process to prevent dust diffusion. Moreover, online sensor monitoring will be used to detect malfunctions in the submarine cable system in real-time, such as monitoring cable temperature. Meanwhile, fiber optic communication system will specify locations of any cable fault. At present, the project is in the pre-construction phase, and the construction will start in 2026 with the scheduled completion of the first circuit in 2028 and the second circuit in 2029.
Investment in energy infrastructure is a vital foundation for the sustainable future of Ko Samui. It will maximize the capability and reliability of electricity supply, a key factor for improving the quality of life of Ko Samui residents, building confidence for investors and entrepreneurs, and declaring Ko Samui’s energy readiness to become one of the world’s Top 10 destinations.