Electric utility information is available in many different places. Below are a few of the best.
Arizona Corporation Commission (ACC)
The ACC maintains a docket of its decisions:
https://edocket.azcc.gov/search
It also keeps annual reports and plans:
https://www.azcc.gov/utilities/electric/electric-annual-reports
Federal Energy Regulatory Commission (FERC)
FERC maintains a record of detailed financial and operations data:
https://elibrary.ferc.gov/eLibrary/search
Form 1 and Form 3 are useful.
Energy Information Administration (EIA)
EIA also maintains electricity data.
https://www.eia.gov/electricity/
Form EIA-861 is among the most useful:
https://www.eia.gov/electricity/data/eia861/
Securities Exchange Commission (SEC)
You can find also find financial and other material information on publicly-traded utilities at the SEC:
https://www.sec.gov/edgar/searchedgar/companysearch
Forms 10-K, 10-Q, and 8-K are annual, quarterly, and informational reports, respectively.