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By Gavin Maguire

LITTLETON, Colorado, July 13 (Reuters) - If the U.S. power sector were undergoing a mid-year physical, the doctor's verdict would be encouraging: vital signs continue to improve, clean energy is steadily gaining strength, and some long-standing ailments are becoming less severe.

The transition is far from complete, but the trend lines remain firmly pointed in the right direction.

What's more, total electricity output continues to grow as the overall system gets cleaner.

Total electricity output from January through June was 2,234 terawatt hours (TWh), according to energy think tank Ember, the highest ever for that half-year period, marking a nearly 3% expansion from the year before.

Much of that growth is driven by AI-hungry data centers and electrification, according to the Energy Information Administration, which expects U.S. power consumption to hit record highs for a third and fourth straight year in 2026 and 2027.

On the surface, the rapid expansion of electricity supply suggests a healthy patient. But a closer look at the following vital signs is needed before declaring a clean bill of health.

VITAL SIGN 1: CLEAN POWER APPROACHING PRIMARY STATUS

The clearest sign of progress is that clean electricity sources are now regularly generating more power than fossil fuels.

From March through May, clean power sources generated over 50% of U.S. utility-supplied electricity, the longest stretch on record, according to Ember.

Even in June, when summer demand boosts gas-fired generation, clean sources still provided a hefty 46.4% of all electricity.

That compares with 42.4% in June 2025 and 41.7% in June 2024, indicating sustained clean-power growth despite the current U.S. administration's aggressive push to promote fossil fuels over renewables.

Diagnosis: The grid is no longer merely adding clean energy at the margins — clean power is increasingly the dominant source during key months of the year.

VITAL SIGN 2: SOLAR STRENGTH

No part of the power system is growing faster than solar.

Solar power output topped 51 TWh for the first time in June, according to Ember, while first-half solar generation reached 231 TWh.

In June 2025, solar generation was around 41.5 TWh, and first-half output last year totalled 190 TWh — a year-on-year growth rate of more than 20%.

Solar's share of the U.S. generation mix has also climbed to new highs, and since March has consistently accounted for more than 10% of the overall utility mix.

Diagnosis: Solar has evolved from a niche contributor into a key pillar of the U.S. power system.

VITAL SIGN 3: COAL CONTINUES TO SHRINK

The sector's oldest chronic condition continues to recede.

Coal's share of generation has dropped from around 32% in early 2016 to just 11.7% in April 2026.

Coal-fired generation in April 2026 totaled only 39.8 TWh, versus more than 113 TWh in January 2016.

High summer temperatures and demand for power-hungry air conditioners have boosted coal-fired generation, but its year-to-date output remains around 11% below year-ago levels.

Diagnosis: Coal remains part of the generation mix, but is no longer a critical resource.

VITAL SIGN 4: POLLUTION KEEPS FALLING

Emissions are responding to the changing generation mix.

Total power-sector emissions in June were just over 146 million metric tons of carbon dioxide and equivalent gases, according to Ember.

That is down from nearly 154 million tons in June 2025, meaning power-sector emissions fell by around 5% from a year ago despite growth in overall electricity output.

Spring 2026 delivered especially strong results, with total emissions of just 114 million tons in March and 109 million tons in April, among the lowest levels in the dataset.

Diagnosis: Cleaner generation is translating into real emissions reductions, not just cleaner capacity additions.

VITAL SIGN 5: NATURAL GAS REMAINS KEY

Not every indicator points to a completed transition.

Natural gas still generated 39% to 44% of U.S. electricity during the first half of 2026.

Gas-fired generation reached 162 TWh in June 2026, underscoring its continuing role in meeting demand and balancing renewable output.

Long promoted as a "bridge fuel," gas remains difficult to displace in the world's top gas-producing country because it can ramp output quickly when demand rises or renewable generation falls.

Diagnosis: The patient is healthier, but still reliant on gas as its primary source of dispatchable power.

CLOSING PROGNOSIS

The mid-year check-up shows an electricity system undergoing a steady transformation rather than a dramatic revolution.

Clean power has crossed important thresholds, solar has become a genuine heavyweight, coal is fading, and emissions continue to decline.

Natural gas remains indispensable, but the direction of travel is unmistakable: with each passing year, the U.S. grid looks a little less fossil-fueled and a little more clean-powered.

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

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