Grid-scale batteries in CAISO earned $2.77/kW-month in April 2026. That is below March's $3.70/kW (-25.1%), and the third sub-$3/kW month so far this year.

Temperatures held within a degree of last April. With weather neutral, price compression came from the supply side: a battery fleet over 16 GW absorbed midday surplus and discharged enough volume after sundown to cap evening peaks, displacing gas from the supply stack.

CAISO wind production rose 32%, hitting new records for peak production supported by the 3.5 GW SunZia wind site coming online in New Mexico.

Solar generation fell 6.5% year-over-year. The two forces squashed both ends of the price spread: the lower midday solar peak raised midday prices, while stronger overnight and evening winds held evening prices below last year's peaks.

​Read last month's report here.

TB4 spreads narrowed from $189/MW to $123/MW year-over-year

Daily average TB4s fell from $189/MW to $123/MW year-over-year. The strongest day of April 2026 was April 4 at $169/MW, which would have been a below-average day in April 2025. The weakest day, April 25, posted just $74/MW.

Most of the losses in battery’s merchant opportunity came on the discharge side.

Evening Day-Ahead energy prices averaged $24/MWh at the 7pm peak, down 43.7% from $43/MWh in April 2025.

Midday charging prices barely moved, edging from -$5.06/MWh to -$5.00/MWh at the 2pm trough.

Unlike last month, the squash in spreads was not the result of higher temperatures.

Average daily highs (66.1°F) and lows (43.2°F) sat within a degree of last April, and heating-degree days came in at 310, marginally above April 2025's 297. With temperatures essentially unchanged, the supply-side mix did most of the work.

Wind production rose by 32% lowering evening prices

Wind production in CAISO rose 31.6%, while Solar generation fell 6.5% year-over-year.

The shift in the renewable mix allowed wind to do more of the work after sundown while solar lagged at midday. The result was a flatter price profile and softer evening peaks.

Monthly average peak wind production set a new record at 5.7 GW.

Part of this is the result of the SunZia site bringing 3.5 GW of Wind production online in New Mexico after 20 years in development.

The combination of Wind and batteries displacing natural gas plants to suppress peak-hour prices is a phenomenon we expect to continue in CAISO’s wholesale market.

Two major offshore wind developments at Humboldt (900 MW) and Morra Bay (2,900 MW) are anticipated to come online in Northern California in the early 2030s. Their additions will continue to suppress peak-time evening wholesale prices in the long-term.

Average net load at its daily minimum deepened to -3.5 GW from -3.0 GW in April 2025. Effective load (net load plus battery charging) rose to 3.6 GW from 2.2 GW. Charging demand grew by 1.4 GW while the net-load trough deepened by only 0.5 GW, so batteries are lifting midday prices on net rather than just following them.

Zonal spreads collapsed in lockstep without converging

TB4 spreads across all three CAISO hubs dropped by a third compared to April 2025. NP15 fell hardest, dropping 37.3% from $180/MW to $113/MW. SP15 fell from $206/MW to $139/MW (-32.6%), and ZP26 from $208/MW to $145/MW (-30.0%). ZP26 still posts the highest spread, and NP15 still the lowest.

The ZP26-NP15 premium widened from $28/MW to $33/MW.

SP15 and ZP26 each see 40% of negative-price hours respectively, compared with 19% in NP15.

The deeper troughs maintain the southern arbitrage opportunity intact, even as absolute spreads compressed. Batteries sited in SP15 and ZP26 still earned the midday charging window that NP15 does not see.

Real-time battery revenues compressed faster than day-ahead

​With battery energy storage capacity in CAISO growing by roughly 5 GW, day-ahead bidding under $50/MWh has become a dominant part of the bid stack in all hours of the day, lowering wholesale prices.

Back in April 2025, Real-Time bidding concentrated charging volume in the midday window and discharge volume into the 6-8pm peak. The fleet largely followed the day-ahead schedule with limited deviation in real time.

Now, in April 2026, midday charge volume rose by 40% during the same hours, and midday discharge volume dropped by two-thirds. The fleet pulled more energy at the bottom of the curve and held it longer; cheap evening discharge bids rose to ~6,000MW at 7pm.

Real-time revenues fell 59.8% year-over-year, more than twice the 27.3% drop in day-ahead, because that shift collided with much weaker FMM clearing prices.

PacifiCorp prices split across East and West at EDAM launch

​EDAM is now live across most of the WECC footprint, introducing PacifiCorp as its first participant.

The primary member of the new western market is split in two BAAs cleared on opposite sides of the seam.

PacifiCorp East’s (PACE) day-ahead prices averaged $6.13/MWh in the first five days after launch, against $19.25/MWh at PacifiCorp West (PACW) and $19.04/MWh at CAISO.