Pacific Gas & Electric Co. wants to raise rates on San Francisco customers to cover the roughly $10 million added to the company’s annual tax bill under a 2018 measure that hikes taxes on the city’s biggest businesses to fund homelessness services.

In a letter the utility company sent to state regulators last month, PG&E argues it should be allowed to recoup its Prop. C tax burden solely from San Francisco customers since its tax bill is “significantly” higher here compared to other places. The company claims that it has to pay “more than $23 million per year” in business taxes to San Francisco. That figure, which includes what Prop. C forces the company to pay, can’t be independently verified because it’s kept confidential by the city treasurer’s office.

PG&E’s proposed rate hike would, the company said, raise monthly bills by about $0.92 for the average residential customer — enough to reel in an extra $9.8 million annually. PG&E has to get permission from the California Public Utilities Commission any time it wants to raise rates.

PG&E spokeswoman Jennifer Robison said in an email that the utilities commission “has provided direction that when a local business tax is substantially higher than the average for a utility’s service area, the additional cost should only apply to customers within the city or county that enacted the tax.” Asking customers outside of San Francisco — who had no say over Prop. C and won’t benefit from it — “would not be just, reasonable or fair.”

PG&E customers will likely see their monthly bills increase by around $4.80 following a separate rate hike that began this month. The company is seeking to raise rates by as much as $30 a month per customer over several years, largely due to the fallout that unspooled after PG&E’s power lines were linked to deadly California wildfires — though the utility is not expected to get every increase it asks for.

City Attorney Dennis Herrera is opposing the prospective Prop. C rate hike, calling the request “inconsistent with (commission) policies and not just and reasonable to San Francisco ratepayers” in a protest letter he sent to the commission.

The commission has at times allowed utilities to raise rates in targeted areas when local governments raise fees that vastly exceed other places. Ordinarily, when taxes go up in one city, a utility company will raise rates across its entire service area to pay for it.

PG&E, Herrera argues, isn’t paying more taxes and fees in San Francisco compared to other cities it operates in. The fee the company pays the city to do business in San Francisco was set in 1939, Herrera said. PG&E pays 0.5% of its gross receipts from the sale of electricity within San Francisco and 1% of its gross receipts from its sale of natural gas — far lower than places like San Jose, Fresno and Bakersfield.

On the whole, Herrera claims there is no evidence PG&E has outsize costs of doing business in San Francisco compared to other places, so it shouldn’t get to target only San Franciscans for a rate hike.

Prop. C — which would raise up to $300 million a year — is earmarked for housing and homelessness services. Voters approved the measure last year. And while the city is collecting the tax, the money is being put on ice until a messy court battle over the measure wraps up. Business-interest groups sued the city over the voter threshold officials used to pass the measure.

A San Francisco Superior Court Judge ruled in the city’s favor, but the business groups have appealed.

“PG&E is once again trying to unfairly single out San Francisco customers,” Herrera said in a statement. “We’re going to do everything we can to ensure that San Francisco ratepayers don’t face an inappropriate hike to their bill.”

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa