The San Francisco-based company, formally named Pacific Gas & Electric, added a rate increase to finance the improvements may be requested, the Oakland (Calif.) Tribune reported Tuesday.
The Metcalf substation in San Jose was the target of rifle fire in April 2013 that caused $15 million in damage and temporarily disabled the substation.
"This was an extremely professional job," said Jon Wellinghoff, former commissioner with the Federal Energy Regulatory Commission, of the shooting. "This was a very professional job. We don't know if this was a probing attack" in advance of a larger attack in the future.
The security upgrades will include opaque fencing surrounding the substations, increased security patrols and advanced cameras, lighting and alarms, PG&E spokesman Brian Swanson said.
"We are likely to be asking for more money," Swanson added. "That would tend to have upward pressure on rates."
No timetables or explanation of costs was given by the utility.