Drought threatens Java island's power supply

"Some hydropower generators are not in operation because of less water," Luluk Sumiarso, director general for electricity at the mines and energy ministry, told Reuters.

"If the drought continues through to November, then that is a vulnerable situation for our reserve electricity generating capacity in Java, because it will fall," he said.

The government had predicted the electricity generating capacity reserve margin could fall to around six percent in November, compared with an acceptable level of around 30 percent, if the drought continued.

The country's annual dry season, which runs from April to October, has been harsher than normal this year.

"At the moment, there is no problem on the supply side. But if there is a disturbance in the electricity system then that is a problem which we can't avoid," Sumiarso said.

State electricity firm PT Perusahaan Listrik Negara (PLN) had 18,000 megawatts (MW) electricity capacity but only around 15,000 MW was in operation, he said. About 1,100 MW come from hydropower and peak demand required 13,000 MW.

Sumiarso said PLN had delayed some power plant maintenance to ensure electricity supply on Java island. He gave no details.

Power demand in Indonesia as whole is estimated to be growing by around 10 percent annually, making it one of the most robust markets in Southeast Asia.