Grid-scale batteries in CAISO earned $2.59/kW-month in August 2026, up 4% from August 2025's $2.50/kW and 38% above July's $1.88/kW.

Gains came entirely from the day-ahead market and ancillary services. Real-time revenue fell 81% year-over-year, as batteries lost -$0.28/kW-month providing energy in the FMM.

These losses are attributed to days where batteries, on aggregate, charged during periods of high Real-Time prices. August 26 provided one example of such a day. Real-time prices peaked above $1,000/MWh in SP15 for several hours after the net load peak.

Some batteries charged during this period, registering as a loss in Real-Time Energy revenues.

​Learn more in the rest of the article.

Key takeaways

• CAISO battery revenues rose 4% year-over-year to $2.59/kW-month, and sat 38% above July.
• Day-ahead energy revenue rose 17%, while real-time energy revenue fell 81%. Fifteen-minute market revenue was negative at -$0.28/kW-month.
• Real-time TB4 spreads rose 56% to $5.17/kW-month, against a 34% rise to $4.54/kW-month in the day-ahead market. The fleet did not capture the wider real-time spread.
• Average demand rose 8% to 31.5GW and the average daily peak 7% to 40.0GW.
• The top five days delivered 28% of the month's revenue, against 25% in August 2025.

TB4 is the spread between the four highest and four lowest hourly prices in a day, reported here as a monthly total in $/kW-month so it compares directly with revenue. IFM is the Integrated Forward Market (day-ahead), FMM the Fifteen-Minute Market, and RTD Real-Time Dispatch (five-minute).

If you have any questions about our CAISO research, please reach out to ovais@modoenergy.com.

Summer price volatility reaches an annual high after a mild spring

Real-time TB4 spreads at SP15 reached $6.37/kW-month in August 2026, up 68% from $3.80/kW-month a year earlier. Day-ahead spreads rose 35% in the same period, from $3.74/kW-month to $5.05/kW-month.

Price volatility in CAISO is high this summer following a milder spring. SP15 FMM TB4’s are averaging $5-6/kW-month, compared to $3-4/kW-month last year.