Vietnam’s Phu Quoc relies on a single undersea cable for 70% of its power, a vulnerability exposed by recent outage

On Nov. 29, crews building a coastal road in Ha Tien drove piles into the undersea line linking the mainland to northern Phu Quoc, cutting electricity to Duong Dong, Cua Can, Cua Duong, Ham Ninh and the entire northern half of the island. More than 30,000 households were plunged into darkness, water supplies were disrupted and hotels scrambled to keep operations running at the start of the holiday season.

To stabilize the grid, An Giang Power rerouted electricity from the south of the island and rushed 20 diesel generators to Phu Quoc, adding about 2.5 MW of temporary capacity. But repairing a damaged submarine cable is notoriously complicated, a process that can take months.

While awaiting full repairs, power crews were racing to build a temporary 110 kV overhead line from the Ha Tien shore to the damage site to restore a stable connection. The line was put in use Friday night.

The largest island of Vietnam has two mainland power sources: a 220 kV line serving the south and the 110 kV submarine cable feeding the north.

The cable, more than 57 kilometers long, has been operating since 2014 and has been crucial to Phu Quoc’s transformation. It slashed electricity costs, ended the island’s reliance on diesel generation and powered a tourism boom that lifted visitor numbers from under 1 million in 2015 to more than 8.3 million in 2024.

But the island’s electricity demand has soared by an average of over 45% per year. To catch up, the record-breaking 220 kV sea-crossing line was completed in 2022, boosting capacity by 500 MW, enough to meet projected needs through 2035.

Even so, experts say the system remains dangerously vulnerable. The two power sources are not linked in a closed loop, meaning electricity cannot automatically reroute when one line fails. So when the submarine cable went down, the island’s larger 220 kV line could not immediately cover the gap.

Several planned 110 kV lines and substations have been delayed for years because of land-clearance issues. Power authorities are urging the province to resolve them quickly, especially with Phu Quoc set to host APEC in 2027, when electricity demand could double.

Local energy officials say rooftop solar for self-use could help relieve strain, though large solar or wind projects require careful study given the island’s limited land. Tourism experts argue that big hotels should be required to maintain backup power capable of operating for 48–72 hours, following models used in places like Hawaii.

They also recommend establishing an island-wide infrastructure security center, similar to those in Japan and South Korea, to monitor electricity, water, telecoms, the environment and transportation in real time and coordinate emergency responses.

The outage, they warn, is a reminder that Phu Quoc’s explosive growth has outpaced its infrastructure, and that the island remains vulnerable to even a single shock.