Pacific Gas and Electric Co.’s main union is pushing back forcefully against efforts to make the company, which is currently owned by investors, controlled by the public instead — something Sen. Bernie Sanders, state Sen. Scott Wiener and the city of San Francisco have proposed in various forms.

Most recently, IBEW Local 1245 shot back at a political advertisement from Sanders that criticized PG&E for its role in causing deadly wildfires. The union, which represents about half of PG&E’s 23,000 employees, released its own video in response, criticized Sanders’ endorsement of a public takeover, saying it would be prohibitively expensive and misguided.

Tom Dalzell, the union’s business manager, noted in the video that his labor group represents not only PG&E employees but also workers at numerous publicly owned utilities in Northern California.

“We know what we’re talking about, and Sen. Sanders, you’re just plain wrong on this,” Dalzell said. “Publicly owned utilities are capable of greatness. They’re also capable of bad management and bad luck, the same as investor-owned utilities.”

The union’s video, which runs about five minutes and 30 seconds, recounts a string of problems involving public utilities, including a series of problems involving Sacramento’s Rancho Seco nuclear power plant, now decommissioned. A narrator later says that “public ownership will not stop climate change.”

IBEW is sharing the video through the union website and an industry trade group and promoting it on social media, Dalzell said.

The Chronicle reached out to the Vermont senator’s campaign, which did not offer comment on the union ad.

In Sanders’ ad, supporters accused PG&E of “decades of negligence” and indicated they wanted the public, not investors, to own the company. Sanders, who leads the Democratic presidential primary’s delegate count, has previously responded to PG&E’s woes by saying that Californians “cannot remain hostage to a profiteering corporation for a very basic human need.” His campaign website includes a survey that encourages people to “support bringing PG&E under public ownership.”

IBEW is also protesting a bill from Wiener, D-San Francisco, that would put control of PG&E in the hands of a new government entity. And the union has fought San Francisco’s attempts to buy the PG&E electric poles and wires that serve the city.

Taken together, the efforts demonstrate the kind of resistance that ideas for complete structural overhauls at PG&E will continue to encounter. Despite PG&E’s responsibility for fires that killed dozens of people and burned communities to the ground, utility labor leaders could prove a powerful supporter of keeping the company intact.

In an interview, Dalzell reiterated his union’s longstanding belief that switching from one kind of energy provider to another, whether going to publicly owned from investor-owned or vice versa, threatens employees’ pensions.

“It’s just hard to have a residual pension in one and start a new pension in the middle of your career somewhere else,” Dalzell said. “The sum does not equal the value of what they would have had if they had stayed somewhere else.”

Dalzell said his members were “furious” about the Sanders advertisement, and those who supported his presidential campaign “felt betrayed.”

The IBEW conflict illustrates some of the difficulty Sanders’ ideas could face between “the campaign rhetoric and the policy implementation side,” said Sonoma State University political scientist David McCuan.

“Campaign rhetoric is passionate,” he said. “The implementation of public policy is difficult, not sexy and riddled with peril.”

The union video is likely to resonate with rank-and-file PG&E workers, but public anger toward the company could easily mount again depending on the company’s performance this year, when it will likely continue shutting off power in an attempt to prevent fires, McCuan said.

Wiener is hoping to tap into that public anger with his legislation, SB917, that would put PG&E under public control. When Wiener announced he was introducing the bill in San Francisco this month, members of IBEW came to his news conference to protest. They held signs with messages such as “Wiener don’t touch my pension,” booed and shouted “lies” at times.

Dalzell recently wrote an opinion piece criticizing the bill that was published on The Chronicle’s website. The union is telling lawmakers about its opposition to the bill as well.

Catie Stewart, a spokeswoman for Wiener, said the bill was crafted with the interests of PG&E employees in mind.

“We’ve designed the entire bill to protect workers and their wages and their pensions and their benefits,” she said. IBEW is “entitled to do whatever they want and oppose this, but it would be really great of them to constructively provide feedback as well.”

The bill was referred to the Senate’s utilities and energy committee but has not yet received a hearing.

Wiener’s bill is advancing at the same time that San Francisco continues with its own efforts to create a full-fledged city-run electric utility. The city offered PG&E $2.5 billion for its local power lines and substations last year and was rejected by the company, which has consistently resisted efforts to chip away at its service area.

San Francisco leaders pledged to press on even after the city’s rejection. This month, the city began an internet campaign called “Our City, Our Power” to drum up public support. In a statement, Mayor London Breed said the city’s offer to PG&E was consistent with residents’ “desire to move our city in a new direction through public power.” The campaign can be viewed online at publicpowersf.org.

But Dalzell’s union already has its own website decrying the idea of a San Francisco local takeover of PG&E. The union website, sfprioritycheck.com, says the city should instead focus its efforts on combating homelessness and property crime and building housing.

J.D. Morris is a San Francisco Chronicle staff writer. Email: jd.morris@sfchronicle.com Twitter: @thejdmorris