All four buildings — the Marco Polo, Pearl One, 1001 Wilder Avenue and The Royal Court — were the focus of an identical study five years ago. Buildings built before 1975 were not required to have automatic sprinklers.

The community task force, which began work in February, is nearly finished drafting a list of incentives to offset the costs. The task force was formed at the direction of the City Council, and consists of business people, construction professionals, firefighters, apartment owners and city building officials.

The costs, however, could make it harder to persuade building residents and homeowner associations to start retrofitting projects.

"That's a one-time cost you can't overcome," said Burt Goldenberg, a 78-year-old retiree from the Marco Polo. "You have to try and get a second mortgage to take care of it. It is a big hit when you are on a fixed income. You have a lot of people who don't have that kind of money."

Jane Sugimura, president of the Hawai'i Council of Associations of Apartment Owners and a resident of Pearl One, said the cost did not sit well with residents of the building. In fact, it didn't when they heard the estimates in 2000.

Now, the cost for each of the buildings surveyed is 50 percent higher than five years ago.

"They didn't like the first number, and they absolutely hate the new one," said Sugimura, a member of the task force. "Their position is: 'No way are we going to agree to this.' It is going to be a hard sell."

Recent high-rise fires — including one that gutted five units in Makiki and another a day later that killed an elderly Waikiki man — have fueled the city's long-simmering debate over sprinkler systems. The Honolulu Fire Department viewed those fires as a potential catalyst for change, just as it did in 2000 when the Interstate Building fire prompted a mandatory retrofit of sprinklers into commercial high-rise buildings.

The new study reviewed the costs for systems made with steel pipes, said Sam Dannaway, president and chief fire protection engineer for S.S. Dannaway Associates Inc., author of the study.

The new estimate would be lower if the systems were made with a kind of sturdy, heat-resistant plastic pipe now used in the sprinkler industry, he said. The exact cost per unit using plastic was not calculated, but Dannaway estimated they would be 20 percent to 25 percent cheaper than the new projections.

Regardless of materials, the jobs remain expensive.

According to the study, retrofitting would cost:

• $4,305 per unit at the Marco Polo on Kapi'olani Boulevard.

• $8,550 per unit at Pearl One in Pearlridge.

• $10,459 per unit at 1001 Wil-der Avenue.

• $13,473 per unit at The Royal Court on Ward Avenue.

"Our prices are based on conventional construction, which is steel pipe," Dannaway said. "Those prices have been affected by the recent boom in the construction industry and the rise in prices of all kinds of construction commodities, including steel and copper."

The solution to the high cost of sprinklers lies in offering incentives, said task force member Ken Silva, who also is the fire department's assistant chief of support services. That could happen shortly after the next meeting on May 13.

Silva said the city council is not currently considering legislation to mandate sprinklers. It will be up to the council to decide if the issue is important enough to act on and whether to incorporate any incentives, he said.

"They would have to decide whether they would want to push it forward," Silva said. "Whether they felt there was a pressing need for it and could they realistically convince their constituents that it was a necessary measure for safety in our community."