In our latest article, "A Bigger Fleet Meets a Windy June", we take a look at what happened to SPP wind generation in June 2026, and it turned out to be a record-setting month. The region averaged roughly 14.3 GW of wind, the strongest June on record, and on two separate days, June 9 and June 27, hourly output climbed into territory that ranks among the highest wind hours SPP has ever recorded in any season, not just summer. For a month when wind typically starts easing off after the spring peak, that's a notable break from the norm, and it's the kind of result that immediately raises the question of whether it was a fluke of weather or something more permanent.

That's exactly the question the article sets out to answer. Installed wind capacity across SPP has grown from under 5 GW in 2011 to roughly 35.5 GW by the end of 2025, more than a sevenfold increase in a decade and a half. That buildout shows up directly in the record books: the single highest wind hour observed each year has climbed almost in lockstep with capacity, from about 3.8 GW in 2011 to an all-time high of 26,199 MW set on December 19, 2025, and SPP's own forecasts now call for hours exceeding 31 GW.

Figure 1| EIA SPP Installed Wind Capacity and Record Observed Output by Year

That capacity growth is only half the story, though, because a good chunk of what the fleet can produce never actually reaches the grid. Adding curtailed energy back into the picture, June 2026's potential wind output reached roughly 15.6 GW on average, another record, and above the metered 14.3 GW figure. In an average recent June, SPP now curtails on the order of 1.2 GW of wind, up from essentially nothing before 2020, mostly due to transmission congestion rather than any actual shortage of wind. That widening gap between generated and potential output is a dynamic that matters directly for real-time price behavior during the windiest hours.

Figure 2 | June Wind: Generated vs. Curtailed Output

There's also a geography angle worth flagging, since growth hasn't been even across SPP's footprint. One zone in the eastern half of the system has done most of the heavy lifting and now accounts for more than half of June's wind output, which has real implications for congestion and basis risk when that much energy has to move out of a relatively confined area at once. The bottom line the article lands on is structural, not seasonal: with capacity still climbing, SPP's wind floor and ceiling are both rising, curtailment risk grows alongside it, and the bar for gas-fired generation to compete keeps moving higher.

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