EGPS in February released its 2024 Renewables Awards newsletter in which we highlighted specific regions and the role that renewable energy (RE), including solar and wind, played over the past year, comparing and contrasting their performance. One category that we examined was market penetration (market share), or the percentage that RE makes up of overall load. The metrics and numbers we showed were annual and we provided a breakdown between solar and wind from the years 2019 to 2024. Except for CAISO, wind has held dominant market share positions compared to solar since 2019, however wind growth has stalled in recent years and solar is showing dramatic growth and in ERCOT is quickly narrowing the gap.  To take this analysis further, beyond annual numbers, we asked what happens over the course of the year, and for that matter, during the day? And has there been change over recent years? This article takes a more detailed look at market penetration for solar and wind to include summer versus winter (i.e. August and January) and time of day (24 hour) and we focus on markets including CAISO, ERCOT, SPP and MISO over time since 2016. 

Figure 1 below shows average load, RE generation, and RE percentage of load for CAISO, ERCOT, SPP and MISO for the months of August 2024 (summer) and January 2025 (winter). The load appears as vertical bars, orange for CAISO, red for ERCOT, blue for SPP, and gold for MISO and green for RE for each RTO. The numerical labels indicate the average RE market share during each hour of the month.

Figure 1| Average August 2024 and January 2025 Hourly Load, RE generation, and RE% Market Share for CAISO, ERCOT, SPP and MISO