Fossil fuels staged a comeback in China’s power sector last quarter, as weather variations and grid constraints slowed the growth of clean energy.

Thermal power output rose 3.7% over the first three months of 2026 after a 1% decline last year, the first yearly drop in a decade. Electricity generation is by far the country’s largest source of greenhouse gases, and the rebound undermines the progress made in reining in emissions ahead of the government’s own targets.

The math behind China’s fossil fuel use is fairly simple. If generation from clean sources grows enough to meet increases in demand, then the country can burn less gas and coal.

However, that did not happen in the first quarter, in part because of the weather. In March, the average wind speed across the country dropped 13%, according to a report from Huafeng Innovation Research Institute. Even though China added a record number of new turbines last year, wind generation over the period fell 2.9%, according to industrial output data. Nuclear also fell 3.8%.

“Limited wind resources in many key regions, and the shutdown of many nuclear plants for maintenance, most likely contributed to the increase in thermal power,” said Trivium China energy analyst Cosimo Ries.

Power demand grew by 5.2% during the quarter, driven by heavy industry and the rapid expansion of electric vehicle charging stations and data centers, according to clean energy think tank Ember analyst Matt Ewen.

CURTAILMENTS WORSEN

The conditions for clean energy generation also worsened because of rising curtailments. The years-long boom in installations has left parts of the grid unable to deal with a surplus of power when the sun shines and the wind blows. China wasted 9.4% of its solar power and 8.6% of its wind power in January and February, up from 6.1% and 6.2% in the same period in 2025.

Much of the increase in thermal generation during the first quarter would have been unnecessary if that curtailed electricity had been available.

China’s grid operators are racing to develop the capacity to absorb more renewables, rapidly building out the energy storage systems and power lines that will allow them to balance supply with demand at any time and in any location.

However, China’s market rules have been designed for a grid dominated by coal-fired power. Regulatory challenges are slowing down the optimal use of the new infrastructure, said Ember analyst Muyi Yang.

“The exponential wind and solar growth of the past few years has started to normalize somewhat this year. Growth is now increasingly shaped by integration constraints.”