South Korea on the Radar: A Cost-Based Pool With No Negative Prices

South Korea is now on the radar — and it is the exception that proves the rule about how the Decke works.

A cost-based pool, not an auction

Most markets we track clear by price bidding. Korea does not. The Korea Power Exchange (KPX) runs a cost-based pool: the hourly System Marginal Price (SMP) is set from the variable cost of the marginal generator, not from competitive bids. We track the official KPX inland SMP — published as a clean hourly table — in ₩/MWh.

What that means for the numbers

• Average: about ₩117/kWh (₩116,788/MWh) over the last seven days
• Range: ₩47 to ₩153/kWh
• Zero negative hours — by design
• Perfect-foresight ceiling (the Decke), 2-hour battery: ₩71,149/MWh; 4-hour: ₩92,105/MWh

Because the price is cost-based, Korea's mainland SMP does not go negative — unlike Britain or Germany. The arbitrage spread comes from the daily cost curve (cheap nights, expensive evenings), not from negative-price events. The Decke still measures the most a battery could capture; it just describes a smoother, positive curve.

A market mid-transformation

That is changing. Under the 2022 New Energy Policy, Korea is moving toward a real-time, bidding-based market with zonal pricing — much of it piloted on Jeju Island, where renewables already bid directly and push day-ahead prices down. Alongside, the government is procuring 540 MW of standalone storage by 2027 through ESS tenders. Today most battery value comes from those tenders, not spot arbitrage — model the contract, not just the spread. Details on the Korea rules page.

See it live: South Korea market radar →