WESM prices rise in December despite higher supply

Electricity prices in the Wholesale Electricity Spot Market rose in December 2025 even as overall power supply increased and demand slightly declined, according to data from the Independent Electricity Market Operator of the Philippines.

System-wide average supply climbed to 20,233 megawatts in December, up 1.2% from the previous month while average demand slipped to 13,440 megawatts, down 0.5%.

The wider gap between supply and demand pushed the supply margin to 4,798 megawatts during the month.

Despite the wider margin, the system-wide average electricity price increased to PHP 4.38 per kilowatt-hour from PHP 3.98 per kilowatt-hour in November.

IEMOP said tighter conditions and price spikes in the Visayas and Mindanao offset easing prices in Luzon, lifting the overall system average.

In Luzon, higher supply and lower demand translated into cheaper electricity in the spot market. Average supply rose to 14,422 megawatts while demand fell to 9,324 megawatts.

Luzon’s average price declined to PHP 2.98 per kilowatt-hour from PHP 3.52 per kilowatt-hour.

In the Visayas, demand growth outpaced supply, narrowing the buffer and raising prices. Average supply increased to 2,524 megawatts while demand jumped to 1,978 megawatts while prices rose to PHP 7.22 per kilowatt-hour from PHP 5.29 per kilowatt-hour.

In Mindanao, supply fell as demand rose, tightening margins further and accelerating price increases and average supply declined to 3,287 megawatts while demand increased to 2,137 megawatts.

Mindanao’s average price surged to PHP 7.82 per kilowatt-hour from PHP 4.99 per kilowatt-hour the previous month.

Because of sustained high prices, the secondary price cap was triggered for 213 trading intervals in the Visayas and 216 intervals in Mindanao.

Each trading interval in WESM represents a five-minute trading period, and the secondary price cap is a safeguard designed to limit excessive spot prices.

IEMOP also reported that the Effective Spot Settlement Price rose to PHP 5.55 per kilowatt-hour from PHP 4.57 per kilowatt-hour.

Spot market purchases accounted for 13.2% of total traded electricity, up from 12.3%. The total value of trades increased to PHP 14.19 billion in December.

On the supply side, renewable energy accounted for 26% of total generation during the period. Coal’s share increased to 56.4% of total generation.

IEMOP said output from wind, solar and geothermal plants also rose during the month. Hydropower generation declined, while natural gas output fell and oil-based generation slightly increased.

Only one market intervention was recorded during the billing period, occurring on Dec. 13 after a technical issue prevented the system from generating real-time dispatch results.

IEMOP said reserve market activity declined in December, with total reserve market transactions falling to PHP 3.92 billion from PHP 4.10 billion.