Power bills surged the most in Oriental Mindoro in June, with the Oriental Mindoro Electric Cooperative (ORMECO) raising residential electricity rates by 23 percent—the steepest increase among the country's off-grid utilities.

Industry data released by the Department of Energy on Monday showed ORMECO's residential electricity rate climbed to P18.29 per kilowatt-hour (kWh) in June from P14.92 per kWh in May, pushing it to the third-highest electricity rate among the country's off-grid distribution utilities.

Only Busuanga Island Electric Cooperative (BISELCO) and First Catanduanes Electric Cooperative (FICELCO) charged higher residential rates at P24.92 per kWh and P19.44 per kWh, respectively. 

While BISELCO remained the country's most expensive off-grid utility, its June rate increased by just one percent from May. FICELCO posted the second-largest monthly increase at 21 percent.

Energy Undersecretary Rowena Cristina Guevara told reporters that June's elevated electricity prices reflected supply constraints and strong electricity demand that forced the dispatch of more expensive power plants.

"The main reason, particularly in the Visayas, is that electricity there is the most expensive because of a supply shortage. We had 21 power plants on forced outage, making the region dependent on imported power from Luzon and Mindanao. The Visayas has also been under yellow alert since May 13, and that has driven prices higher," Guevara said.

"For the rest of the country, demand was also high during the summer months. As a result, we had to dispatch more expensive power plants to avoid blackouts," she added.

The supply pressures pushed the entire country to post Southeast Asia's highest average residential electricity rate in June at P12.43 per kWh, narrowly overtaking Singapore by 0.093 centavos per kWh.

"To be accurate, we were the highest in Asia only for the month of June. We monitor this every month," Guevara said.

Of the remaining off-grid utilities, Palawan Electric Cooperative charged P12.93 per kWh, followed by Province of Siquijor Electric Cooperative at P12.86 per kWh, Occidental Mindoro Electric Cooperative at P12.62 per kWh, and Tablas Island Electric Cooperative at P11.95 per kWh.

Marinduque Electric Cooperative charged P11.24 per kWh, followed by Batanes Electric Cooperative (BATANELCO) at P11.23 per kWh, Bantayan Electric Cooperative (BANELCO) at P11.11 per kWh, and Masbate Electric Cooperative at P10.65 per kWh. 

BATANELCO and BANELCO were the only off-grid utilities to post lower residential rates in June, declining by 12 percent and 9 percent, respectively.