​June 2026 was the first summer month of the year to bring heatwaves to MISO, and two of them drove distinct periods of elevated prices. Real-time four-hour top-bottom (TB4) spreads fell year over year at all eight hubs, most by 30% or more.

Solar generation rose 50% and wind rose 15% against flat demand YoY, flattening the daily price range. Michigan Hub led real-time at $277/MW-day, down from $379/MW-day, and Indiana Hub, the reference hub, fell to $256/MW-day from $377/MW-day.

The exception came at month-end: a late-June heat dome pushed Indiana Hub real-time prices to $685/MWh on June 30, more than 20 times the $31/MWh median hour, and provided batteries their single biggest revenue evening of the month.

Key takeaways

• Real-time TB4 spreads fell year over year at every MISO hub, North and South, most by 30% or more. Michigan Hub led at $277/MW-day; Indiana Hub, the reference hub, fell to $256/MW-day from $377/MW-day.
• Solar generation rose 50% year over year and wind rose 15%, while coal fell 13% and gas fell 6%. Demand held flat at an hourly mean of 84 GW.
• Two heatwaves concentrated the month's volatility. Indiana Hub real-time prices peaked at $685/MWh on June 30 when system demand hit its monthly high of 124 GW.
• Real-time regulation averaged $19/MW-day, up 10% year over year. That kept it the highest-paying ancillary product for MISO storage, far above real-time spinning and supplemental reserves at $1/MW-day or below.

Real-time spreads narrowed in MISO as solar rose 50%

Real-time TB4 spreads fell year over year at all eight MISO hubs and can be driven by extreme weather events, like Winter Storm Fern. Michigan Hub led at $277/MW-day, down 27% from $379/MW-day. Indiana Hub, the reference hub, fell 32% to $256/MW-day from $377/MW-day.

The compression ran deepest in the North. Minnesota Hub dropped 56% to $162/MW-day and Illinois Hub fell 48% to $179/MW-day. Southern hubs started lower and fell less in dollar terms: Louisiana Hub declined 33% to $123/MW-day and Arkansas Hub fell 46% to $91/MW-day.

Part of that year-over-year drop reflects a high 2025 base, not only more renewables. A late-June 2025 heat dome over June 20 to 24 set record temperatures across the Upper Midwest and lifted MISO North spreads that month.

Day-ahead spreads moved the other way at the two northern hubs, the only hubs to widen year over year. Indiana Hub's rose 15% to $253/MW-day and Michigan Hub's rose 10% to $240/MW-day.

For a 100 MW, four-hour battery, the split changes where value sits. Real-time swings compressed across the system, while the day-ahead shape stayed strong at the northern hubs. Scheduled arbitrage stayed attractive at Indiana and Michigan even as real-time narrowed.

Supply shifted toward solar and wind across MISO

Solar generation averaged 7 GW in June 2026, up 50% year over year. Wind rose 15% to 10 GW. In total, renewables added 3.5 GW of average output against flat demand.

With demand flat at an hourly mean of 84 GW, the extra renewables displaced fossil output rather than serving new load. Coal fell 13% year over year to 23 GW, and gas fell 6% to 27 GW. Nuclear rose 16% to 11 GW.

That displacement flattened the daily price curve. More midday solar lowered daytime prices and softened the evening ramp, narrowing the hour-to-hour range. Indiana Hub's evening peak averaged $109/MWh in June 2026, down 23% year over year.

Demand held flat year over year at an hourly mean of 84 GW, so the drop came from the supply side, not weaker load.

Two heat events delivered the month's value

Renewables narrowed the everyday shape, but two heat events supplied the volatility that defined battery value in MISO.

The first was the mid-June East Coast heatwave on June 10 and 11. Consequently, real-time prices averaged $98/MWh on June 10 and $128/MWh on June 11, well above the $41/MWh monthly mean, with a real-time peak of $581/MWh on June 11.

The larger event was the late-June heat dome on June 29 and 30. It built over the central and eastern US in the final days of the month. Warnings went out on June 28, and the heat built first in the Midwest, with extreme humidity, before spreading east.

June 30's 7 PM hour cleared $685/MWh, more than 20 times the $31/MWh median hour, while most other hours across June sat below $35/MWh. Revenue depended on being charged and available for a handful of evenings.

The generation mix shows storage doing exactly that. MISO batteries charged overnight, deepest around 2 AM, and discharged into the evening, with average discharge peaking at 458 MW in the 7 PM hour.

Regulation stayed the only ancillary product worth holding capacity for

Real-time regulation averaged $19/MW-day, up 10% year over year, holding its position as the highest-paying ancillary product for batteries in MISO. Day-ahead regulation cleared near real-time at $17/MW-day.

Reserves were low to begin with and fell further. Real-time spinning reserve averaged $1/MW-day, down 57% year over year, and real-time supplemental reserve averaged $0.2/MW-day, down 90%. Day-ahead spinning and supplemental reserves stayed low as well.

What June meant for MISO storage

June brought narrower spreads for most of the month, with two sharp exceptions. More renewables flattened the daily shape and narrowed real-time spreads across all eight hubs, while the mid-June East Coast heat and the late-June heat dome delivered the volatility that defined battery revenue.

The 50% year-over-year jump in solar against flat demand narrowed everyday real-time spreads across MISO North and South. The day-ahead shape held up at the northern hubs and therefore the scheduled charge-and-discharge window stayed wide.

For storage operators, the month rewarded being charged and available for the handful of heat-driven evenings that carried it. In addition, regulation stayed the ancillary product worth withholding capacity for, as reserves cleared near 0.