Koh Phangan's power supply: the aging undersea cable, outage risk and what a villa buyer should check

How reliable is mains power on Koh Phangan, and is an upgrade coming? Power reaches the southern islands (Samui, Phangan and Tao) through submarine cables from the mainland. EGAT describes the existing Samui cable system as ageing and frequently malfunctioning, with a planned 230 kV replacement scheduled for 2028-2029. Until then, outage risk is a due-diligence item rather than a footnote.

What the sources say

• Existing system. EGAT states that Koh Samui has no power plant of its own and is supplied from EGAT's Khanom Substation (Nakhon Si Thammarat) through the Provincial Electricity Authority's submarine cable system: two 115 kV and two 33 kV circuits with a combined capacity of 174 MW. The cables are described as ageing and often malfunctioning, so they cannot always deliver full capacity.
• Outage pattern. EGAT notes frequent outages, especially in April-May peak season, with rolling blackouts and mobile generators as temporary measures. Phangan is served from the same southern-islands system.
• A precedent. In March 2021 an anchor strike was reported to have damaged the 115 kV Khanom-Samui cable, cutting supply to parts of Samui and Phangan to about half of requirements until repairs finished that week (Bangkok Post).
• The upgrade. EGAT says the Cabinet approved on 28 February 2023 two 230 kV submarine circuits (about 50 km) from Khanom to a new Samui substation, adding 400 MW. Construction is slated to start in 2026, with the first circuit due in 2028 and the second in 2029. These are planned dates, and large infrastructure projects often slip. The project is aimed at power instability on Samui, Phangan and Tao.

What it means for a villa buyer

• Assume short outages. Budget for a backup plan, particularly if the villa has a well pump, pool pump, or if you rent it out and guests expect air-conditioning and wifi.
• Backup options. A petrol/diesel generator is cheapest upfront; battery storage with solar can ride through outages. See off-grid solar and battery storage and the PEA rooftop solar buyback scheme.
• Water depends on power. Pumps and storage tanks turn an outage into a water problem; see water supply and shortage risk and groundwater well permits.
• Verify the connection itself. Confirm the meter exists, is in the seller's name and is the right phase; see utilities on Koh Phangan. Remote plots may need a costly line extension.
• Ask locals. Ask neighbours and the current owner how often power drops at that specific location, since outages vary by feeder line.

Takeaway: mains power on Phangan is generally available but depends on ageing undersea infrastructure. A replacement is approved and planned for 2028-2029; until it is built, price a backup system into your purchase and check the specific plot's connection.