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Commission questions whether Transbay cable reduces need for in‑city gas turbines
Summary
SFPUC heard ISO staff and PUC power managers on the Transbay Cable project and whether new transmission can reduce reliance on standby combustion turbines; ISO emphasized mandatory N‑1‑1 reliability criteria and said transmission and local generation planning are complementary.
The San Francisco Public Utilities Commission on April 24 received a technical briefing from the California Independent System Operator and PUC power staff on the proposed Transbay Cable transmission project and related in‑city generation needs.
Barbara Hale, assistant general manager for Power, said the ISO is reexamining the project’s technology choice (from classic HVDC to newer DC‑Light/DC‑Plus) and asked the PUC to consider the study the ISO is preparing after Supervisor Maxwell requested additional analysis of demand projections and transmission alternatives.
Larry Tobias, senior regional transmission engineer for the California ISO, told the commission that reliability criteria — including a federally mandated “N‑1‑1” test that models loss of major facilities during peak hours — drive the need for combined approaches. “We are in that state today,” Tobias said, describing current vulnerabilities when major circuits are out of service.
Commissioners pressed whether adding transmission capacity could obviate the need for in‑city combustion turbine (CT) installs in Bayview‑Hunters Point and Potrero. Tobias and staff said transmission alone would not meet the city’s reliability criteria without complementary generation and distribution reinforcements; however they agreed schedules and planning assumptions can change the relative need for CTs.
Cost and environmental tradeoffs were central to the discussion: commissioners noted that CTs are cheaper to site but higher‑emitting per megawatt, while a 400‑MW Transbay Cable was estimated in the staff packet at roughly $300–$400 million. Commissioners urged staff to present detailed comparative cost and emissions analyses when the item returns for action.
Public commenters from Bayview‑Hunters Point urged the commission to avoid siting polluting CTs in neighborhoods already bearing environmental burdens; other community members said updated planning and transmission investments could enable more renewables in the long run.
The commission took the item as discussion only and directed staff to continue coordination with ISO and return with further analysis for a future meeting.
