​Real-Time TB4 spreads in PJM averaged $317/MW-day in August 2026, 78% above August 2025. The month set no temperature or peak demand records. The higher spreads came from a higher baseline load.

Mean hourly demand rose 8.4% year-on-year to 108 GW, while peak demand fell 0.8%. That is the inverse of July, when average demand slipped 1% and the peak set an all-time record.

Modo Energy's virtual BESS (vBESS) benchmark estimates that a 100 MW, 4-hour battery earned $13 to $15/kW-month across ComEd, Dominion and Penelec. That is little change from August 2025. The gains from wider spreads were partly offset by regulation, which fell to its third-lowest level since the October 2025 redesign.

Key takeaways

• Batteries earned $14.32, $15.08 and $13.47/kW-month in ComEd, Dominion and Penelec.
• Day-Ahead energy took a larger share of revenue than a year earlier in all three zones, up 9 to 22 percentage points, while regulation's share fell.
• Real-Time TB4 spreads averaged $317/MW-day, up 78% year-on-year. Day-Ahead reached $276/MW-day, up 70%.
• Mean demand rose 8.4% to 108 GW while the peak fell 0.8%. Virginia alone drove a third of the increase, with load up 17.6%.

Day-Ahead energy took a larger share of the revenue stack

A 100 MW, 4-hour battery earned $14.32/kW-month in ComEd, $15.08/kW-month in Dominion and $13.47/kW-month in Penelec.

Day-Ahead energy contributed more than a year earlier in every zone: 36.5% of ComEd's revenue against 27.2%, 51.3% of Dominion's against 29.8%, and 37.0% of Penelec's against 24.0%.

Regulation moved the other way. It is still the largest single stream in ComEd and Penelec at 53% of revenue, but that is down from 67% and 71% a year earlier.

Regulation cleared $87/MWh in August against $186/MWh in July, yet regulation revenue fell only a third. Dividing revenue by the clearing price shows why: the 100 MW battery cleared roughly 12 MW of regulation in ComEd, up from 8.2 MW in July.

As energy spreads normalized, the optimizer moved capacity back to the market paying more per MW. Held continuously, regulation at August prices pays $64.81/kW-month, against $9.83/kW-month for a single daily energy cycle at August's Real-Time TB4.

Volume caps the revenue opportunity for ancillary services. PJM procured an average of 729 MW of regulation RTO-wide in August, within a 550 to 750 MW band, so one 100 MW battery at full rated power would be 14% of the entire market.

Higher baseline demand, not acute events, widened the spread

Demand growth lifted both ends of the price curve, but not equally. In Real-Time, the average of each day's four highest hours rose 60% year-on-year to $103/MWh. The four lowest rose 19% to $24/MWh. The gap between them is the Real-Time TB4 spread, which widened 78% to $317/MW-day.

Gas met the largest share of PJM’s load growth, rising 3.1 GW year-on-year. That covered 37% of the 8.4 GW increase in demand. Lower exports freed up another 20% of that increase, with coal, renewables and other sources making up the rest. Dispatching gas further up the merit order is what steepened the curve.

Within the past year, August was middling. Its $317/MW-day ranks eighth of the last twelve months, and July's $895/MW-day is still the highest in the series.

The year-on-year step is what stands out. August 2025 cleared $178/MW-day, the lowest in the series. Nine of the last thirteen months have cleared above $300/MW-day, in a persistently tight PJM.

Where did the demand growth come from?

Virginia was the largest source of load growth. Load in the Dominion zone, which covers most of Virginia, averaged 18.6 GW, up 17.6% year-on-year and 18.4% on two years, contributing a third of PJM's entire increase.

AEP added 9.4%, or 14.2% over two years. ComEd has been flat for three consecutive years.

Spread growth followed the same geography. Dominion's Real-Time TB4 rose 135% to $447/MW-day, the fastest in PJM. Washington DC (PEPCO) rose 132% to $454/MW-day, and Baltimore (BGE) posted the highest absolute level at $463/MW-day. ComEd rose 38%, the slowest of the western zones.