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

LITTLETON, Colorado - The U.S. power system is on track to produce more electricity from clean power sources than from fossil fuels for the third straight month in May, establishing a record-long stretch for clean power generation in the country.

Clean power sources provided the majority of U.S. electricity supplies for the first time in March of this year, according to data from think tank Ember, and extended that run in April thanks to record renewable energy output.

The lowest natural gas-fired generation total in three years also helped ensure clean energy's majority share in April, and further declines in gas power output so far this month look set to keep that trend going in May.

Greater demand for air conditioning systems over the summer may force utilities to elevate fossil fuel-based output from June onwards.

But the current three-month stretch of clean power dominance marks a new milestone in U.S. energy transition efforts, and highlights a growing adeptness within generation networks at maximising clean energy output while curtailing fossil fuel use.

CLEAN MAJORITY

After generating 50.5% of U.S. utility-supplied electricity in March, clean energy sources accounted for 50.8% of electricity in April, Ember data shows.

Big year-over-year increases in output from solar farms (+33%) and hydro dams (+24%) helped lift total clean electricity output by 8% in April from the same month a year ago.

Gas-fired electricity generation in April was 6% lower than in the same month in 2024, further helping to stack generation trends in favour of clean power.

So far in May, data from LSEG indicate that clean energy sources continue to have the upper hand.

From May 1 through May 27, LSEG data shows that solar power output is up by 19% from the same dates in 2024, to a record 883,000 megawatt hours (MWh).

That increase in solar output helped offset a 7% year-over-year decline in output from wind farms so far this month, and helped push total supplies from renewable energy sources to a new record.

On the fossil fuel side of the output ledger natural gas underwent a further year-over-year contraction, with gas-fired output at just under 4.3 million MWh for the May 1-27 window, and the smallest for that period in at least three years.

Coal-fired power output showed a modest 2% expansion so far in May from the same month a year ago, but overall fossil fuel power output is on track for a 9% fall from May 2024.

FOSSIL FLUX

The sustained high price of natural gas - which is the largest single power source within the U.S. electricity system - has been a supportive factor behind the recent clean streak.

So far in 2025, benchmark U.S. Henry Hub natural gas futures have averaged $3.70 per million British thermal units (MMBtu).

That average price is 77% above where Henry Hub values averaged over the same period of 2024, and means that power generators were motivated to cut back on gas use whenever possible so far this year.

Utilities with generation portfolios that contain renewable power were able to deploy maximum volumes of clean energy while curtailing gas-fired production, thereby saving on costs while lifting the proportion of clean power to new highs.

Power generators with more limited renewable supplies opted to boost coal-fired generation sharply higher so far this year, which also provided scope for cuts to the use of pricey gas.

Total generation from gas-fired power stations is down around 8% so far this year from the same dates in 2024, while coal-fired plant production is around 15% higher, according to LSEG.

SUMMER STRAIN

Power generation from solar farms - which have been by far the fastest growing energy source in recent years - looks set to hit fresh highs as the U.S. summer kicks in.

Solar's share of the overall electricity generation mix appears on track to climb from just under 11% in April to around 12% to 14% in the coming months as solar radiation levels peak.

However, greater use of power-hungry air conditioners will put utilities on the hook to ensure that power supplies meet the heightened demand levels, even when the sun doesn't shine.

That will likely serve to lift the proportion of fossil fuels within the overall generation mix, and potentially push clean power's share below 50% again during the hottest months of the year.

But with solar and battery storage capacity still expanding within U.S. networks, clean power's share of the generation mix should remain close to 50%, and could re-emerge as the primary power source once demand for cooling systems dips in the fall.

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

(Reporting by Gavin Maguire; Editing by Sonali Paul)