US CURTAILMENT TRACKER: CAISO curtailments reach record in March, systemwide curtailments hit nine-month high

Wind and solar generation curtailments reached a record high of 606.178 GWh in March and systemwide curtailments reached a nine-month high as renewable capacity rise nearly 6.5% from a year ago, according to California Independent System Operator data.

The March curtailments surpassed the previous record set in April 2022 by nearly 2%, were up 31% year over year and jumped 197.2% month on month, according to CAISO data. Curtailments typically increase in spring as longer days provide more solar generation and seasonal weather changes increase wind generation.

"Based on month-to-date data, April curtailments will top March," said Morris Greenberg, senior manager with the low-carbon electricity team at S&P Global Commodity Insights.

April outlook

So far this month, curtailments have totaled 581.397 GWh through April 23, an increase of 17.6% from the same period a year ago, CAISO data showed.

Midday loads have been quite weak due to behind the meter solar output and natural gas generation has held up relatively well during midday hours when prices are close to zero, Greenberg said, adding large hydro generation has been surprisingly flexible given high runoff. CAISO net exports have increased in April with some hours above 5 GW.

SP15 on-peak balance-of-the-month traded around $59/MWh on the Intercontinental Exchange April 25, a nearly $3 premium to the day-ahead package. In power forwards, SP15 on-peak April averaged $42.82/MWh in its last month, 14% higher than where the 2022 package averaged a year ago, according to S&P Global data.

The six- to 10-day outlook indicates a greater probability for above-normal temperatures across most of California with equal chances for above- and below-normal along the coast, according to the US Climate Prediction Center, a branch of the National Weather Service.

Renewable capacity

CAISO's installed renewable capacity increased 625 MW month on month to 28.135 GW by the end of March, a jump of 6.4% year over year, according to CAISO's March Key Statistics report. Solar generation accounted for 59% of all renewable capacity and wind made up 28.3%, with the remainder coming from geothermal, small hydro and biofuels.

Solar-powered generation averaged 14.2% of the total market share in March, down nearly 4 percentage points from a year ago, while wind-powered generation averaged 11.1% of the mix, little changed year on year, according to CAISO data.

At the same time, CAISO peakload increased 1.5% year on year to average 26.638 GW in March.

Battery storage

As renewable capacity has risen, so have battery installations. CAISO's installed battery capacity was 4.515 GW by the end of March, a jump of 65.5% from a year ago, but unchanged for the third month in a row, according to CAISO's March Key Statistics report.

"Batteries are absorbing a significant amount of energy typically charging by up to 2,000 MW and discharging up to 3,000 MW during evening hours," Greenberg said.

More than 1 GW of battery capacity should come online before summer peak demand, he added.

Curtailment breakdown

S&P Global's systemwide renewable generation curtailment index showed CAISO wind and solar curtailments averaged about 2.386 GW in March, a jump of 120% from February and an increase of 26% year on year.

There are two types of curtailments: systemwide curtailments that occur when there is an oversupply and localized curtailments that occur when the amount of power from one transmission point to another is controlled for congestion management.

Systemwide curtailments reached a nine-month high of 31.15% in March. Localized curtailments made up 68.85% of all renewable curtailments in March, down nearly 22 percentage points from a month ago, according to CAISO data.

As renewable curtailments climbed, spot power prices dropped month on month. SP15 on-peak day-ahead locational marginal prices decreased 6% to average $62.25/MWh in March, according to CAISO data.