Ownership reported to EIA Form 860. Percentages reflect reported generator-level ownership share, averaged when a plant has multiple generators.
Grid context
NERC Region
WECC
Balancing Authority
Arizona Public Service Company
What this means
Battery storage facilities don't generate electricity — they store it. They charge from the grid (often from solar during the day) and discharge during peak demand or to firm up renewables. EIA classifies them as power plants because they connect to the grid like one.