The global energy transition displayed a stark duality in September 2025, as a record-breaking surge in solar power generation clashed with the stubborn persistence of coal consumption across major economies.
New data released by the International Energy Agency (IEA) reveals a complex landscape where rapid renewable deployment is racing to keep pace with rising demand and shifting weather patterns, challenging the linear narrative of decarbonization.
Solar Ascendant: The New Heavyweight
According to the report, total net electricity generation in Organisation for Economic Co-operation and Development (OECD) member countries reached 906.0 terawatt-hours (TWh) in September 2025. While fossil fuels retained a dominant 48.4% share of the mix, the momentum clearly lies with renewables, specifically solar photovoltaics.
Electricity generation from renewable sources climbed 5.9% compared to the previous year, contributing 35.2% of the total supply. This growth was propelled almost entirely by a massive 23.5% jump in solar output, adding 18.8 TWh to the grid.
“The acceleration of solar capacity, particularly in the Americas and Europe, is beginning to reshape the midday supply curve,” noted energy analyst Sarah Jenkins. “However, the variability of weather-dependent resources remains a critical hurdle for grid operators.”
The data underscores this volatility: While solar boomed, hydroelectric power generation slumped 4.0% across the OECD, exposing the grid’s vulnerability to hydrological droughts. This decline effectively muted some of the gains made by wind and solar, forcing grid operators to lean on traditional baseload sources.
The Stubborn Persistence of Coal
Despite global pledges to phase down carbon-intensive fuels, coal-fired power generation demonstrated remarkable resilience. While natural gas usage retreated, dropping 1.5% year-on-year, coal generation filled the void, rising 2.8% in September.
On a year-to-date basis, the trend is even more pronounced. During the first nine months of 2025, electricity generation from natural gas fell 1.0% across the OECD, while coal generation increased by 4.3%. This resurgence suggests that for many nations, energy security and affordability continue to take precedence over immediate emission reductions.
The divergence is sharply regional. OECD Europe successfully reduced coal generation by 10.2% in September, continuing its policy-driven pivot away from solid fuels. In contrast, both the OECD Americas and Asia Oceania regions saw coal usage spike by more than 6%, driven by industrial demand and the need to compensate for expensive or constrained gas supplies.
Climate Volatility Strains Hydro Resources
The interplay between changing climate patterns and energy security was most visible in Chile. The South American nation faced a severe hydrological deficit in September, recording a 19.4% drop in hydro generation.
To maintain grid stability, Chile was forced to ramp up coal-fired power generation, which rose 10.4% over the first nine months of the year. This scenario highlights a growing feedback loop for the energy sector: as climate change impacts water availability, countries with heavy reliance on hydro may be forced back toward fossil fuels to keep the lights on.
Nuclear Stability and Divergent Strategies
Nuclear power, often cited as a critical low-carbon baseload technology, remained broadly stable, dipping just 0.2% year-on-year to 144.4 TWh. However, the aggregate number hides significant strategic shifts among member nations.
Japan continues to aggressively restart its nuclear fleet to bolster energy independence, leading the OECD with a 13.5% year-to-date increase in nuclear output. Conversely, Belgium saw a precipitous 22.6% drop over the same period, reflecting ongoing phase-out schedules or maintenance outages.
Global Implications for 2025 and Beyond
The September data paints a picture of an energy system in flux. Total electricity production increased by 2.0% in the first nine months of 2025, signaling that global electricity demand is growing faster than efficiency gains can offset.
While the 23.5% growth in solar is a technological triumph, the parallel 4.3% year-to-date rise in coal usage serves as a reality check for policymakers. As the Northern Hemisphere enters the winter heating season, the reliance on fossil fuels suggests that the "peak coal" narrative may face further delays before a definitive decline begins.
The IEA’s latest figures suggest that without rapid advancements in energy storage to mitigate the dips in hydro and the intermittency of solar, fossil fuels will remain the grid's primary insurance policy for the foreseeable future.
By Michael Kern for Oilprice.com
