CAISO Demand Response Rule Set to Add 2 GW to Day-Ahead Market as Solar Restructures Merit Order
A CAISO demand response revision due August 19 could add 2 GW of behind-the-meter capacity to the day-ahead market, extending solar-driven bearish pressure.
A revised demand response framework that CAISO was due to release on August 19 (2026-08-19) could add as much as 2 gigawatts of behind-the-meter resources to the day-ahead stack, according to Advanced Energy United's lead regulatory official for the western United States. CAISO NP15 spot power stood at $48.75 per megawatt-hour as of Saturday, August 22, with SP15 at $48.57/MWh — prices that give gas-fired peakers thin margins above fuel costs at current NYMEX Henry Hub front-month levels of $2.77 per million British thermal units.3
Those price levels reflect a grid where solar has already restructured the merit order. EIA data show utility-scale solar generation in CAISO surpassed natural gas output across the first five months of 2026, with solar production up 21% against the same period in 2024 while gas generation fell. Solar bids at zero marginal cost, displacing gas units that had previously set day-ahead clearing prices through the midday and early afternoon hours.1
The demand response revision would extend that pressure into additional hours. Advanced Energy United characterises the change as an accounting adjustment that reclassifies behind-the-meter assets in ways that make wholesale participation economic for load aggregators who previously found the compliance pathway too costly. Two gigawatts would be a meaningful addition on a grid where solar saturation already pushes midday day-ahead prices toward zero in spring and early autumn.3
These are not new generation assets. The rule formalises existing load flexibility by changing how it is classified and compensated, and actual clearing volumes will depend on how fast aggregators complete regulatory approval, telemetry compliance, and contract requirements. Initial enrolment after the August 19 (2026-08-19) release will almost certainly land well below the 2 GW ceiling.3
Advocates have backed the revision. But generators with existing positions in the CAISO day-ahead market have raised concerns about how intermittently dispatched behind-the-meter assets interact with dispatch sequencing. The record available ahead of the August 19 release did not include CAISO's response to those objections.3
One month of data from the Extended Day-Ahead Market illustrated how uneven the CAISO footprint already is. Valley Electric Association, a Nevada entity inside CAISO not subject to California greenhouse-gas regulation, had barely 2.8 GW at peak and a limited internal generation stack. Utilitydive reported its day-ahead clears were among the spikiest in early May 2026, with intraday price swings far larger than the hydro-influenced PACW area produced.2
That unevenness complicates any aggregate bearish forecast for CAISO day-ahead. Behind-the-meter resources concentrate in California's larger load centres, not in smaller entities at the grid's edge. Consistent, predictable dispatch would compress midday price spreads across southern California. Yet if the aggregated portfolio proves intermittent or difficult to forecast in the day-ahead window, the effect is more intraday volatility of the type EDAM data have already shown can be unevenly distributed across the footprint.2,3
Low fuel costs keep gas units viable in peak evening hours when solar fades, with NYMEX Henry Hub front-month holding at $2.77 per million British thermal units as of August 22. But with solar now the dominant generation source in CAISO for the year to date, the share of hours in which gas actually sets day-ahead clearing prices has shrunk significantly. Enrolment figures in the weeks after the August 19 (2026-08-19) framework release will be the first real measure of aggregator speed; if compliance timelines run long, the 2 GW potential may not reach clearing prices before solar seasonally retreats.1,3