COLUMN-US fossil fuel electricity output and emissions hit 2025 peaks: Maguire

By Gavin Maguire

LITTLETON, Colorado, Aug 27 (Reuters) - There's good news and bad news for climate trackers following U.S. power generation and emissions trends.

The good news is that electricity production from fossil fuels likely peaked for the year in July when annual demand for air conditioning hit its highest, and has already started to retreat as cooler temperatures cut power demand.

The bad news is that July's fossil generation peak was the highest monthly total in nine years, and yielded the largest U.S. monthly power sector emissions toll since August 2021.

The mixed bag of generation and emissions milestones underscores the uneven progress of U.S. energy transition efforts, and highlights the central role that coal and gas-fired power plants continue to play in the U.S. generation system.

Yet the jagged nature of monthly generation trends also masks the continuing progress being made across the U.S. power system, where clean power supplies have generated a record share of total electricity so far this year.

Below are more key data points marking the ups and downs of fossil fuels and clean energy sources within the U.S. power generation system.

SUMMER TOPS

U.S. fossil fuel-fired electricity generation peaks during July and August due to the higher levels of electricity demand during those months from air conditioners.

Between 2015 and 2024, July marked the high point in U.S. monthly fossil fuel generation eight times, while August marked the monthly high point twice.

In 2025, July again looks set to be the high water mark for fossil generation due to the number of heatwaves that prevailed over much of the country that month, and the slightly cooler average temperatures that have been registered since.

July's fossil fuel electricity generation total of roughly 290 terawatt hours (TWh) was the highest monthly fossil-fired generation total since August 2016's total of 294 TWh, data from Ember shows.

The July total was 3% more than the generation total of the same month in 2024 (which was also the annual fossil output peak last year), and led to the discharge of 191 million metric tons of carbon dioxide (CO2), Ember data shows.

That was the largest monthly power emissions total since July 2021, and so seemingly reversed a years-long trend of declining overall emissions within U.S. electricity production.

CONCEALED CLEAN PROGRESS

The upswing in fossil-fired generation and emissions this year has stoked fears of backsliding among U.S. electricity producers with regard to clean energy generation momentum.

However, even as fossil electricity supplies scaled multi-year highs in July, the share of fossil fuels within the overall U.S. electricity generation mix has declined to record lows so far in 2025.

Between January and July, fossil fuels accounted for an average of 56% of total U.S. utility-supplied electricity.

That generation share compares to nearly 57% for the same months in 2024, and is well down from a nearly 67% fossil share for the January to July period of 2015.

On the flip side, clean energy sources generated a record 44% share of U.S. electricity so far in 2025, which compares to only a 33% share during the same months a decade ago.

The share of clean power within U.S. electricity generation tends to dip to annual lows at the end of summer as solar generation drops off, but then stages a strong rebound through the winter as wind speeds pick up at wind farm turbine level.

Similarly, the use of fossil fuels within generation tends to drop off during periods of mild weather, such as during the fall and spring, thereby allowing utilities to make maximum use of the clean power sources at their disposal.

The speed of clean power generation growth is likely to slow going forward in response to U.S. President Donald Trump's sudden scrapping of clean energy incentives.

But the overall footprint of clean generation sources continues to expand as existing projects are completed.

That momentum should be enough to lift clean power's share of the U.S. electricity generation mix to new highs for 2025, even as sporadic flare-ups in gas and coal power output underscore the still-dominant status of fossil fuels.

The opinions expressed here are those of the author, a columnist for Reuters.

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