PNW · 8-K · 20261106PR000055

Transmission Capacity Expansion

PINNACLE WEST CAPITAL CORP · 2026-11-06 · Importance 64 · Surprise 42

APS’s transmission plan identifies more than $6 billion of cumulative transmission investment through 2035 to support reliability, resiliency, new resources, and access to out-of-state generation and additional markets. The planning-period buildout includes more than 600 miles of 345-kV-and-above lines and more than 300 miles of 230-kV lines. Projects in development include Helios to Milligan, Pinnacle Peak to Ocotillo, and the Cotton Transmission Corridor, with listed in-service dates ranging from 2027 to 2031.

Key facts

• Pinnacle West’s Cotton Transmission Corridor projects include approximately 80 miles of 230-kV lines estimated in service in 2030/2031 and approximately 29 miles of 500-kV lines estimated in service in 2031. source
• Pinnacle West’s Helios to Milligan project is approximately 23 miles of 230-kV transmission, estimated in service in 2027. source
• Pinnacle West’s Pinnacle Peak to Ocotillo project is approximately 50 miles of 230-kV transmission, estimated in service in 2030. source
• Pinnacle West plans more than 600 miles of 345-kV-and-above transmission lines and more than 300 miles of 230-kV lines in the planning period. source
• Pinnacle West’s proposed transmission for new gas generation is listed as TBD, with a 2030 in-service estimate. source