Coming into the summer there were questions all around about how the PJM grid would fare.  The expansion of data centers around DC and the growth of crypto facilities threatened to produce further structural load increases in the continuation of the pattern that has been playing out not only in PJM but in other areas around the country.  Conversations swirled in PJM’s Reserve Certainty Senior Task Force meetings about the potential shortfalls of the ISO’s reserve requirements with adjustments being made throughout the spring and summer.  On the other side of the equation, PJM shared in the explosive growth in installed solar capacity along with the rising renewable market in MISO and continued buildout in the more established CAISO and ERCOT fleets.  With the summer now in the rearview mirror, it’s a good time to look back over the past few months at where the changes were focused, and the impacts to net demand. 

Figure 1 | Monthly Total Cooling Degree-Days, June-September 

In the lead-up to the heart of the summer, Mother Nature delivered plenty of heat to PJM territory.  The heat was most pronounced in western PJM—a theme which carried through the rest of the summer.  The figure above plots monthly total cooling degree-days for the Ohio Valley from June through September over the past eight years.  In June, total CDDs added up to 312, well over the 8-year average of 254.  In July temperatures reverted to the norm.  This continued for PJM as a whole deeper into the summer during August and September, but not so with western PJM.  Ohio Valley CDDs came in above average in August and September (by 11% and 19%, respectively) while CDDs for PJM as a whole were brought down by cooler weather along the coast.  We can see the impact of the warm temperatures in western PJM in the regional load breakout.  The figure below shows 12x24 average hourly load for the system as a whole and then for a selection of different BAs allocated to PJM regions.  Load was very strong in June across all three areas, with a smaller year-on-year increase present in July.  By August and September load was falling down to match 2023 levels in the Mid-Atlantic region and then dipped significantly below the past two years for September with the cooler temperatures prevailing.  Likewise, South region (Dominion) load closed the gap to 2023 levels in September.  By contrast, West region load widened the year-on-year gap during the past month.