The weather pattern in Southern California is delivering some solar volatility as the cloud cover and precipitation pattern is swinging the midday volume across Southern California. The recent activity is showing up in the day-ahead and real-time market hourly price settles as the spread between the two gen hubs has collapsed with SP15 moving up to meet that of the strong NP15 midday prices. 

Figure 1 | CAISO Day-Ahead Auction Settle Breakdown – Heavy Load

The table above is a breakdown of the day-ahead auction results from CAISO where the numbers represent the heavy load block of hours as this is the period that carries the solar profile.  We have highlighted March 5^th, 2025 as it displays the point listed in the opening paragraph where NP15 settled in at $54.75 while SP15 trailed by a couple of dollars ($52.77).  The price delta was driven mainly by line losses as the marginal congestion component (MCC) pushed down to zero most hours (see Figure 2 below).