The governor also chose Liane Randolph, 49, the general counsel at the California Natural Resources Agency, to fill Picker's former seat, making all five PUC members Brown appointees.
Picker, 62, replaces Michael Peevey, a former Southern California Edison Co. president and leader for the last 12 years of the 1,000-person bureaucracy.
The PUC oversees electric and gas utilities, private water companies, intrastate rail, livery and bus services, ridesharing operators and some telecommunications providers.
"Michael Picker's deep experience and sound judgment make him uniquely qualified to take on this role," Brown said in a statement. "Liane Randolph has handled very difficult issues with insight and balance and will be a real asset to the commission."
In an interview with The Times, Picker called the PUC "an enormously challenging organization" where "people are starting to respond slowly to the need for change."
The commission's number one priority going forward, he said, would be safety. Picker said he would move quickly to create a full investigative team and to designate an internal safety advocate as well as external advisors, possibly from the University of California.
Picker recently took a lead role in getting commission approval of new programs to boost enforcement for violations of electric transmission and rail safety rules.
Deficiencies in the PUC's safety programs became starkly evident in September 2010 when a
Peevey, 76, announced in October that he would not seek a third, six-year term.
By nominating Picker, Brown is signaling that he wants "fresh eyes" to help steer the state toward its goal of getting a third of its power from renewable sources by 2020.
The governor may also be seeking to distance his administration from criticism directed at Peevey.
Peevey has become a lightning rod for public anger, particularly in Northern California, since the San Bruno disaster.
Peevey also has become embroiled in a related controversy involving improper communications and conversations between Peevey and at least one other commissioner and top PG&E executives.
Such contacts violate PUC rules that require all communications be shared among all parties in a commission legal proceeding, such as a rate-setting case or an accident investigation.