LITTLETON, Colorado, April 17 (Reuters) - The U.S. power system is on track to hit a new energy transition milestone in April as total clean electricity supplies approach their annual peak while overall electricity demand eases during the so-called spring shoulder season.

Clean power sources generated more than half of all U.S. electricity supplies for the first time in March, accounting for 51% of all utility-scale electricity output that month, according to data from energy think tank Ember.

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But this month clean power could notch up an even larger share of the U.S. electricity mix if overall power use declines in line with normal seasonal trends to allow utilities to cut output from fossil fuel plants just as renewable output rises.

Lower fossil fuel supplies alongside the likely annual peak in combined wind and solar output could push clean power's share of electricity output to new highs for April, and ensure that energy transition momentum is maintained in 2025.

DEMAND DIP

April traditionally marks the annual low point for electricity consumption in the U.S. as it lies between the power-hungry winter and summer seasons when demand for heating and cooling systems peaks.

For the past seven straight years, April marked the low point for monthly electricity consumption in the U.S., according to Ember, and that trend looks set to be extended in 2025 as mild temperatures have lowered heating demand so far this month.

At the same time, the month of April tends to mark the high point for the share of electricity production from U.S. solar and wind farms, as wind output tends to peak just as annual power demand hits a lull.

In April 2024, clean power sources accounted for a then-record 49% of total electricity supplies, a high point that was only exceeded last month.

Combined output from solar and wind farms accounted for a 23.5% share last April, and then scaled a new high in March of this year with a 24.4% share.

The share of electricity from wind farms alone was 15% in April last year, and hit a new record of 15.2% in March of 2025 as wind speeds picked up at turbine level this spring.

SLOW START

During the first half of April 2025, total U.S. wind power production was down by around 7% from the same period in 2024, according to LSEG.

Below-normal wind speeds in key locations have muted overall wind generation so far this month, with output in the Electric Reliability Council of Texas (ERCOT) - the largest U.S. wind production hub - down around 3% from a year ago.

And the latest wind output forecasts for the rest of the month call for wind output at or below long-term averages in major wind farm zones, including in ERCOT.

However, with overall power use set to remain curtailed due to lower heating demand, even average levels of wind output should be sufficient to help clean power sources increase their overall share of the U.S. generation mix.

At the same time, output from U.S. solar farms is set to climb to new highs across every major power market, thanks to higher installed capacity and more daylight in key solar markets such as Texas, California, Arizona and Nevada.

This combination of higher solar production alongside average wind output should help push clean power's share of the U.S. generation mix above 51% for April, and ensure that the U.S. power system continues to set new milestones in 2025.

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

https://www.reuters.com/business/energy/us-power-system-primed-scale-new-clean-milestone-april-maguire-2025-04-17/