Key Takeaways
- China curtailed 360 TWh of wind and solar electricity in the first half of 2024 – a 49 % rise year‑on‑year – enough to power the UK or Mexico for over a year.
- The wasted renewable output would have covered all of China’s electricity demand growth in the period and allowed coal generation to fall, yet coal‑fired output rose 3.4 % instead.
- Structural overcapacity stems from continued coal‑plant construction (30 GW commissioned, 274 GW in the pipeline) and long‑term contracts that guarantee coal a share of demand regardless of cheaper clean power.
- Transmission bottlenecks prevent moving wind and solar from resource‑rich western regions to eastern industrial centers, compounding curtailment.
- Battery storage is repeatedly cited as the solution to absorb midday surplus and release it when needed, with successful examples in Chile and Bulgaria.
- Similar curtailment trends are emerging in Australia, Japan, and India, indicating a global challenge as renewable build‑out outpaces grid infrastructure.
Curtailment Figures and Impact
In the first six months of 2024 China turned away 360 terawatt‑hours (TWh) of wind and solar power, according to a joint analysis by the Centre for Research on Energy and Clean Air (CRECA) and Global Energy Monitor. This amount represents a 49 % increase compared with the same period in 2023 and equates to roughly the annual electricity consumption of the United Kingdom or Mexico. Had that power been utilized, it would have fully satisfied the growth in China’s electricity demand during the half‑year and permitted a reduction in coal‑fired generation. Instead, coal output rose 3.4 % year‑on‑year, reversing a decade‑long decline and underscoring the scale of the waste.
What Curtailment Means
Curtailment occurs when grid operators must switch off wind turbines or solar farms, or refuse to accept their output, because the transmission network lacks capacity to accommodate the electricity at that moment. Electricity cannot be stored on a wire; any power produced but not consumed instantly is lost. Consequently, the fossil‑fuel plants that could have been displaced continue to run, emitting carbon dioxide and other pollutants while clean energy sits idle.
Root Cause: Ongoing Coal Expansion
Researchers identify the continuing coal‑building programme as the fundamental driver of overcapacity. In the first half of 2024 China brought 30 gigawatts (GW) of new coal‑fired capacity online – the most for any first‑half period in a decade and 43 % higher than in 2023 – while retiring only 2.7 GW. An additional 25.4 GW began construction, and a staggering 274 GW remain in various stages of planning, representing roughly 22 % of the existing coal fleet. This persistent expansion creates a system with more generating capacity than can be utilized.
Market Mechanisms Locking in Coal
Even as coal plants operate fewer hours, long‑term power purchase agreements guarantee them a share of demand. This year, coal generators are expected to sign annual contracts covering 60‑70 % of the electricity they delivered in the previous year. Such capacity payments effectively reserve space on the grid for coal, irrespective of how much cheaper wind or solar power is available at any given time. As Qi Qin of CRECA notes, the coal buildout is a warning about overcapacity, not a blueprint for energy security.
Transmission Bottlenecks Exacerbate the Problem
The geographic mismatch between renewable resources and demand centers intensifies curtailment. China’s largest wind and solar farms are located in the deserts and grasslands of the north and west, whereas the bulk of electricity consumption occurs in the industrial east. Transmission lines have not been built quickly enough to move the surplus westward power eastward. Yuan Ren of Wood Mackenzie describes the curtailment pressure as structural, predicting it will persist through the rest of the decade unless grid infrastructure catches up.
Policy Signals and Their Contradictions
In April the central government urged tighter control of both coal capacity and generation, leading to a sharp slowdown in new coal‑plant permits—only 8.6 GW approved in the first half of 2024. Nevertheless, developers proposed 70 GW of new coal projects and revived another 20 GW during the same period, a quarter more than in 2023. Christine Shearer of Global Energy Monitor observes that policymakers are sending mixed messages: they call for restraint on coal while market mechanisms continue to guarantee coal significant electricity sales and capacity payments.
Discrepancies in Official Reporting
The government’s National Energy Administration (NEA) reports far lower curtailment rates—8.6 % of solar output and 9.1 % of wind output—for the first half of 2024. The CRECA/Global Energy Monitor analysis, which uses weather‑adjusted data to capture unreported generation, finds a much higher 26.1 % curtailment rate. The NEA ceased publishing monthly province‑by‑province curtailment figures in March and did not respond to requests for comment, raising concerns about transparency and the true scale of the waste.
Effects on Renewable Investment
The persistent curtailment has dampened enthusiasm for new solar projects. New solar installations in China fell 66 % year‑on‑year in the first half of 2024, a decline driven both by grid constraints and a policy shift that removed the guaranteed fixed‑price feed‑in tariff previously enjoyed by renewable generators. Investors are increasingly turning to projects that pair photovoltaic panels with battery storage, allowing excess midday generation to be saved for evening use rather than wasted.
Global Parallels
China is not alone in facing curtailment challenges. Australia’s National Electricity Market curtailed 2.93 TWh in the first half of 2024, a 37 % increase and equal to 7 % of its wind‑solar output. Japan’s grid rejected 2.35 TWh, up 34 %, while India curtailed 8.13 TWh in the quarter ending June—about 14 % of its solar production for that period. Across these regions, the common theme is a renewable build‑out that has outpaced the development of transmission and storage infrastructure.
The Role of Battery Storage
Analysts and researchers consistently highlight batteries as the key to mitigating curtailment. By storing surplus electricity generated during peak solar hours and discharging it when demand is high or renewable output falls, batteries smooth the supply‑demand imbalance that forces operators to curtail clean power. Chile’s experience illustrates this potential: in 2025 the country added 4 GWh of battery capacity, more than doubling its installed storage, with most new systems co‑located alongside solar plants, thereby reducing curtailment. Bulgaria offers another example of effective storage integration. Scaling such solutions worldwide could transform the current waste of renewable energy into a reliable, low‑carbon power supply.