CAISO Solar captured -$1.7/MWh in spring 2026
Between March and May 2026, CAISO solar captured a generation-weighted average price of -$1.7/MWh.
A negative capture price means solar, on balance, lost revenue in the wholesale market across the season.
A note on methodology - and why solar would choose to lose wholesale revenue
Capture prices are the generation-weighted average price that solar sites receive per unit of energy sold to the wholesale market.
This article estimates solar capture prices by scaling zonal generation profiles to each site’s rated power. This creates estimated site-level solar generation profiles.
These estimated site-level profiles are multiplied by the Day-Ahead price at seen at each site, and divided by total generation, to calculate the average capture price.
Capture rates are the ratio between this solar capture price and the average nodal price, known as the around-the-clock (ATC) price. This ATC is what a baseload generator would receive for producing 24/7.
These metrics only capture wholesale market activity. They do not account for out-of-market revenues, such as PPAs or Federal Tax Credits, that these sites likely receive.
Incentive payments drive solar to continue exporting to the market even when it is uneconomical to do so.
Capture rates dipped to -38% in April 2026, leading spring to settle at an average of -13%. This is a decline from Spring 2025’s average capture rate of +1.2%.
Spring is consistently the weakest season for solar wholesale revenue in CAISO.
Heating and cooling load vanishes in response to milder weather, while daylight hours extend and lift solar output. Midday supply runs well ahead of demand. The result is that, year over year, Californian power prices regularly dip below zero throughout the season.
Negative prices grow shallower as Solar raised its offer floors
Five months into 2026, CAISO has logged 516 hours of negative Day-Ahead prices. While this surpasses 2025, the magnitude of these negative prices has grown shallower.
Average negative prices in spring 2026 settled at −$5.5/MWh, compared to −$9.8/MWh in 2025 and −$14.6 in 2024. The magnitude of negative pricing has roughly halved each year.
Solar sites offer power at negative prices to maintain revenues from pay-as-produced PPAs.
These sites typically earn $20-$30/MWh under long-term power purchase agreements from utilities, who pay for zero-carbon generation to meet California's Renewable Portfolio Standards (RPS) mandate.
On top of these contracts, projects claiming the full federal production tax credit (PTC) from the Inflation Reduction Act earn close to $30/MWh for the first ten years.
These contracts only pay out if the site exports. To ensure they continue exporting, sites will submit negative offer prices.
These incentives have led to deep negative prices in the past.
But comparing CAISO’s offer curves between seasons shows that fewer offers are being submitted with the deeply negative floors seen in previous springs.
Offers between -$150/MW and -$30/MW fell from 60% of midday solar offers in spring 2025 to 37% in spring 2026.
That volume reappeared just below zero: the -$5 to $0 band jumped from under 1% to 22%. The “PTC-floor” band, between -$30 and -$5, barely moved and still holds the largest single share at 37%.
Since Solar continues to set the marginal energy price during the midday surplus, the shallowing depth of these negative prices tracks against the rise in offer floors.
Curtailment rises to 4.8 GW in Spring 2026
Despite its growing renewable fleet, CAISO’s solar output has stagnated.
Average peak generation reached 17.3 GW this spring, just 400 MW more than peak generation last year.
This meager uplift in Solar output is largely the result of higher curtailment. Average peak curtailment jumped to 4.8 GW in Spring 2026, up by 1.7 GW compared to last year.
CAISO is increasingly importing power rather than sending its own midday surplus out. In the first five months of 2026, CAISO doubled its imports from neighboring systems and net generation fell 19% year on year.
These power sources are cheaper for the ISO to import: recovering post-drought Pacific Northwest hydro and the new 3.6 GW SunZia wind project in New Mexico, which CAISO began importing from in April.
With cheaper energy flowing in and less room to push surplus out, more of California's solar generation has been curtailed within the state.
Northern solar average $7.2/MWh capture prices, as lower solar penetration reduces cannibalization
Solar in the north earns far more than solar in the south. NP15 was the only CAISO zone with positive solar capture prices in Spring 2026, at $7.17/MWh, while ZP26 fell to -$1.98 and SP15 to -$3.63.
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