Back in December 2021, we first tackled the question of how much natural gas the CAISO battery fleet was displacing. We wrote a special report titled ‘Batteries Just a Drop in Gas Burn Bucket’ and declared it was safe to hit the snooze button on the issue for a few more years. The capacity of the CAISO fleet was only 2.6 GW and peak discharge from the fleet was less than a gigawatt on the average evening. Our best estimate for gas displaced by batteries then was around 0.01 BCF a day. Flash forward to July 2023, we checked in again in a special report titled ‘CAISO Batteries’ Impact on Power Burns’. By this point, the fleet’s capacity had almost doubled and the peak evening discharge for an average evening had more than tripled. Still, the impact on gas wasn’t large, averaging less than 0.08 BCF a day displaced. Ultimately, we credited batteries with around a third of the year-on-year drop in power burns with other factors playing a larger role. Now, a year later, we’ll take another look at the growth in the fleet and our current best estimate of the amount of gas displaced as of July 2024.

First, let’s check in on power burns and review some important context for CAISO this spring. The figure below displays year-on-year power burns for both PG&E and SoCal with the 2024 gas year in blue and 2023 in yellow. SoCal saw a large year-on-year drop in power burns between March and mid-June this year. Congestion between NP15 and SP15 meant an abundance of solar and extremely low midday prices for SP15 for much of this spring. PG&E power burns varied, coming in below last year’s levels in March and April, but mostly above 2023 in May and June. A variety of factors including transmission outages, a good hydro year, solar growth, and more impacted both PG&E and SoCal burns this year. However, we will attempt to tease out how much of the loss can be attributed to batteries.

Figure 1 | PGAE and SoCal Power Burns Year-on-Year