San Francisco could face a cost of more than $20 billion to take over its local electric grid, PG&E CEO Patti Poppe said. The utility’s estimate is far above the $3.4 billion value the city assigned to PG&E’s electric equipment in a filing with state regulators in April.

Poppe said PG&E’s figure includes costs the city has not factored in, such as separating San Francisco’s system from the rest of the utility’s grid. She said that work would require a new substation and service center.

City officials disputed PG&E’s estimate and said they would keep pressing their purchase plan before the California Public Utilities Commission. PG&E is expected to give the commission more detail on its estimate next week. San Francisco’s yearslong effort to buy the local infrastructure drew renewed interest after a December substation fire caused widespread outages.