KPX Expands Transmission Outage Reflection in Day-Ahead Plans
Korea Power Exchange (KPX) expanded the scope of transmission line outages reflected in day-ahead generation plans, lowering the threshold from 10 days to 2 days in November 2024, after initially starting with 10 days in October 2024. This change significantly increases the number of outages influencing daily electricity prices.
Our take
Is grid maintenance becoming an unchecked driver of Korea's wholesale power price (SMP)?
Yes: grid outages are now a regular input to day-ahead prices rather than an exception, and no market body reviews them for their price effect, so SMP becomes harder to forecast, not uniformly higher or lower.
Reflecting outages a day ahead brings dispatch closer to the physical grid, which in that sense makes the price more accurate. Against that, the outage schedule is set by KEPCO, which is also in effect the single buyer in the wholesale market, KPX checks outages only for system security, and a price already fixed for a cancelled outage is not recalculated. The direction of the effect depends on which generators are excluded from price setting, so what decides whether this stays a manageable risk is whether outage review is given to the power market supervisor now under discussion, and whether one-day outages are added.
What the source says
- Korea Power Exchange (KPX) began reflecting transmission outages lasting 10 days or more in day-ahead generation plans starting October 2024.
- In November 2024, KPX further lowered the reflection threshold to outages lasting 2 days or more.
- Out of 4604 total outages in the first half of 2025, 529 cases (12%) lasted 10 days or more, while 2303 cases (50%) lasted 2 days or more.
- KPX is considering a further expansion to include one-day outages in day-ahead generation plans.
- The Shin-Gapyeong substation outage in September 2026 saw SMP drop by 56 KRW/kWh, with nearly 10 additional LNG generators excluded from price determination, yet the already determined SMP was not recalculated when the planned outage was canceled.
- Private power generators criticize the structure where KEPCO, as the single buyer, plans transmission maintenance without external verification of necessity or duration, leading to market price suspicions.
- A KPX official stated that the exchange only assesses grid stability during maintenance, not the market appropriateness or fairness of KEPCO's actions.
- Professor Jeon Young-hwan argues that if outage plans affect market prices, they must be supervised, calling for transparency in KEPCO's decision-making and proper market oversight.
For investors — Solar and wind developers and their lenders: for revenue linked to SMP, treat grid outages as a separate source of price variance in downside cases, especially in regions with thin transmission, and do not assume a cancelled outage reverses a price already set.
Merchant storage investors and optimisers: outage-driven price moves are a trading opportunity only if outage schedules are visible before day-ahead prices are fixed; whether they are published in advance is not stated, so confirm this before counting it as revenue.
Watch: Monitoring the progress of discussions and legislative actions concerning the establishment and specific mandate of the proposed Electricity Market Regulator regarding supervision of transmission outage impacts on market prices.
Weekly digest
What changed in Korea's power market this week — one email, every week.
Email only, used solely to send this digest (delivered via Resend). Unconfirmed sign-ups are deleted after 30 days. Free.