- South Korea’s nuclear power output surged 8.7% in the first half of 2025, outpacing targets due to fewer maintenance outages.
- Nuclear’s rising share has lowered coal imports and costs, though transmission bottlenecks continue to limit both coal and renewable power deployment.
South Korea’s nuclear power generation is racing ahead of official targets due to fewer maintenance outages, new capacity, and reactors running at full tilt, cutting coal use and helping rein in electricity costs.
Nuclear output grew 8.7% year-on-year in the first half of 2025, far exceeding the government’s 2.9% annual growth plan, while coal-fired generation plunged 16%, data from state-run Korea Electric Power Corp (KEPCO) showed.
“The basic principle of generator operation in the power market is minimising generation costs. Nuclear power generally has lower fuel costs than other generation sources such as coal and liquefied natural gas (LNG),” the Korea Power Exchange (KPX) said. “If nuclear and renewable facilities continue to expand, generation from gas and coal is likely to continue to decrease.”
KPX said a 29% decline in outage times and a 6% increase in nuclear capacity also boosted supply. The 1.4 gigawatt Shin Hanul #2 reactor southeast of Seoul began operations in April 2024.
South Korea, Asia’s No. 2 nuclear power generator after China, now operates 26 reactors with 26.05 GW of capacity and is building four more, including two units totalling 2.8 GW due online in 2026. Nuclear output has risen 6.1% annually since power demand stabilised in 2022.
President Lee Jae Myung, who took office in June, has pledged continued support for nuclear power. KEPCO data showed that nuclear’s share of power generation rose to 31.7% in 2024 from 25.9% in 2019, offsetting most of coal’s drop to 28.1% from 40.4%.
That shift cut South Korea’s energy import bill, with coal imports falling 8% annually on average from 2022 and the coal import bill dropping 23% to $15.4 billion last year, customs data showed.
“Plenty of coal plants are sitting idle not by choice, but because there’s no spare capacity on the transmission lines to carry more power,” said Seunghoon Yoo, energy professor at the Seoul National University of Science and Technology.
Transmission constraints have also capped renewables, which, along with hydropower, contribute just over a tenth of South Korea’s generation, well below the global average of 30%, the Institute for Energy Economics and Financial Analysis said.
Power demand growth has slowed as industrial use declines, with cooling requirements driving most consumption since 2022. KPX said gas-fired plants increasingly operate only at morning and evening peaks, avoiding midday when demand dips.
The energy ministry said rising electricity use from data centres and semiconductor plants has not yet affected fuel procurement.