Korea manages Chuseok low-demand period without solar curtailment
During the Chuseok holiday (September 25-26, 2026), Korea's grid experienced significantly reduced power demand, with peak demand falling to 56.2 GW on September 25. Despite initial forecasts predicting potential solar oversupply requiring curtailment, cloudy weather reduced actual solar generation, allowing the Korea Power Exchange to operate the grid stably without output controls.
Our take
Is Korea's solar curtailment risk easing after a curtailment-free Chuseok holiday?
Korea's solar curtailment risk has not eased, since the holiday avoided curtailment only because cloud and warmth held solar down and demand up, and the operator's plan for a sunny holiday was still to curtail.
The curtailment plan was drawn up alongside the demand-raising measures, so those measures were not expected to close the gap on their own. What would change the verdict is fast-responding flexibility such as storage on clear low-demand days.
What the source says
- The actual maximum demand on September 25 exceeded the power authorities' forecast of 49.9 GW due to higher-than-expected temperatures.
- On September 25 at 10 AM, the minimum demand within the power market was 45.3 GW, with total demand including PPA and self-consumption solar reaching approximately 50.8 GW.
- Ministry of Climate, Energy and Environment The Ministry of Climate, Energy and Environment is operating an 'Autumn Low-Demand Period Power Supply Stabilization Countermeasure Period' from September 19 to November 15, 2026.
- The main challenge during autumn low-demand periods is responding to potential oversupply and grid instability caused by sharply reduced power demand and increased renewable energy generation.
- Kim Sung-jin Korea Power Exchange (KPX) Chairman Kim Sung-jin emphasized close cooperation with government and related agencies to manage power supply and demand without inconvenience to citizens during the remaining holiday period.
- Korean government Electric vehicle charging fees were discounted from 11 AM to 2 PM daily between September 24 and 27 to stimulate charging demand.
- Korea Power Exchange KPX is utilizing AI-based power demand forecasting and a Cloud Movement-based PV Forecasting System (CMV) to precisely predict solar generation variability.
- On September 25 at 12 PM, operating nuclear capacity was 20.7 GW, coal was 10.5 GW, and LNG was 11.1 GW, all reduced compared to four weeks prior.
For investors — Solar developers should model curtailment on clear, low-demand days in spring, autumn and holidays rather than on annual averages, and not read one cloudy holiday as lower risk.
Merchant storage investors and optimisers should treat clear low-demand middays as where flexibility is most needed, but not count that need as revenue while the size and payments of plus demand response are not given.
Watch: Announcement of new grid management strategies or forecasting system upgrades by the Korea Power Exchange for future low-demand periods.
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