San Francisco’s appalling homeless problem seemed to worsen only modestly compared to the rest of the Bay Area when the city released its preliminary homeless-count numbers in May. The first glimpse showed a 17% uptick — not great, sure, but not as bad as Alameda County’s 43% rise. Or Santa Clara’s 31% increase.

Turns out the news wasn’t quite so rosy.

The final report released Friday, in the middle of a holiday weekend, shows that the street-count increase would actually be 30% if the city had used the same standards for counting as it had in past years.

San Francisco now has 9,784 unhoused residents compared with the last biennial count taken in 2017 of 7,499, according to the report. But the city pegged the latest total, based on a one-night tally taken in January, at 8,011, the same number revealed in the May report.

That preliminary May number was calculated using federal guidelines that don’t include people the city has traditionally counted in jails, hospitals and rehabilitation facilities — a tradition the city is now ending.

By sticking to federal guidelines instead of the broader definitions San Francisco has used for many years, 1,773 people are excluded from the count total.

The additional tally of 1,773 people is still in the 76-page report. But it’s in a supplemental section on page 66.

Several regional and statewide homeless policy directors welcomed San Francisco’s switch to the U.S. Department of Housing and Urban Development’s guidelines, but San Francisco’s leading homeless advocate said she thought it wasn’t the right move.

“We really need to compare apples to apples,” said Jennifer Friedenbach, head of the San Francisco Coalition on Homelessness. “The helpfulness of the count is that we are comparing those apples to apples, so at least we’re comparing year to year — but now that’s not entirely the case.”

Like most other homeless policy experts, she said the biennial one-night “Point In Time” counts are inaccurate, since there’s no way even an army of volunteers can find every homeless person in a city in one night. But at least it is a yardstick.

“I would guess that politics entered that decision, because they could have made that decision in years past,” Friedenbach said. She and other community homeless policy advisers, she said, have long advised using as broad a definition of homelessness as possible in the count, “so now they’re choosing not to have the most complete count possible.”

City homeless programs chief Jeff Kositsky said the change was made to be more consistent with other cities and counties in the Bay Area, which have long used the tighter count guidelines set by HUD. That consistency became increasingly important this year as the region’s nine counties began a push to coordinate their homeless efforts with each other, and Gov. Gavin Newsom made regional cooperation a focus of his homeless strategies.

“We just have decided for practical purposes we are going to stick with the HUD definition and do the rest of the numbers in an appendix,” said Kositsky, director of the city Department of Homelessness and Supportive Housing. “The methodology for doing these counts gets super confusing, and most people want to compare us to other communities. So using our own definition is just not helpful.”

Kositsky denied that politics dictated the decision and said his intention is to be more comprehensive, not less. He noted that he added more than two dozen homeless-aid programs to those surveyed for this year’s homeless count.

One of his counterparts across the bay in Alameda County — where the biennial count went up 43% — said she thought the switch made sense.

“There is lot of talk about coordinating regionally, and if you’re apples to apples we can see better how the changes are impacting all our communities,” said Elaine de Coligny, head of the county’s leading nonprofit on homelessness, EveryOne Home. “It’s just beneficial for all of us to be talking about these things in the same terms. It’s good to use the same data definition.”

Despite the surge in the street count, San Francisco’s count showed both improvements and backslides in some categories.

Veterans homelessness went down 11%. The number of chronically homeless individuals — the most severely troubled, on the streets more than a year — went up 35%. The total of 612 people in families without homes was virtually the same as in 2017.

About two thirds of the increase in unsheltered homeless people is attributed in the report to people sleeping in about 600 cars, RVs or vans — a growing vehicle problem reflected in many other counties up and down the state.

Kositsky said as disappointing as the total count is, he sees hope in the array of improvements he is putting into place.

He noted that he plans to open a Vehicle Triage Center in the coming year, where people can park and get city help finding housing, and after adding 400 units of permanent supportive housing since 2017, the city now runs one half of the entire stock of supportive housing in the Bay Area.

“We have a lot of work to do, but we’re doing it,” he said.

As co-chair of the statewide Homeless and Supportive Housing Advisory Task Force, Sacramento Mayor Darrell Steinberg is in charge of trying to coordinate regional homeless efforts. He said San Francisco’s change to HUD guidelines was a good one.

“It’s not an effort to game anything,” he said. “The methodology on these counts is evolving, and it’s actually getting better. What people really want to know is what is being done to address the problem.

“I’d say what San Francisco has done is an effort to be more consistent.”

Kevin Fagan is a San Francisco Chronicle staff writer. Email: kfagan@sfchronicle.com Twitter: @KevinChron