Struggling to fulfill a campaign promise made last fall by virtually every Florida lawmaker, the Legislature approved a series of measures Monday that would reduce home insurance rates -- modestly, for the most part -- by having the state take on billions of dollars in additional insurance risk.

Insurance costs soared here after eight hurricanes hit the state in 2004 and 2005 and forecasters predicted that ferocious storms could keep hitting for at least the next decade. Easing the crisis is Gov. Charlie Crist's top goal, and he convened a special legislative session to address it within days of taking office on Jan. 1.

But while Mr. Crist, a Republican, and the Republican-dominated Legislature said last week that they were committed to significant across-the-board rate reductions, reality proved more complicated.

South Floridians covered by the state-run insurer of last resort because private companies refuse to insure their homes will see the smallest savings -- as little as 8 percent. Their insurance costs have as much as tripled since 2004, forcing many people to consider leaving Florida.

Homeowners with private insurance would save more -- up to 21.8 percent, on average -- according to legislative analysts.

''We don't claim that the bill is perfect,'' said State Senator Bill Posey, a Republican from Rockledge who helped negotiate the changes during a weeklong special session in Tallahassee, ''and we don't claim that the work is done.''

The legislation would allow private insurers to buy backup coverage from the state's Hurricane Catastrophe Fund at below-market rates and, in turn, require them to reduce premiums. But a major storm -- or worse, a string of them -- could not only wipe out the fund but also force residents to pay steep yearly assessments on home, auto and other insurance policies to make up for it.

''The catastrophe fund's resources will wind up being drained more frequently than ever,'' said Robert P. Hartwig, the president and chief economist of the Insurance Information Institute, a trade group in New York. ''What's really happening here is that people are being obligated to pay massive assessments in the future.''

Insurance companies nationally enjoyed record profits in 2006, which saw no devastating hurricanes, and Mr. Crist has strongly criticized the industry, an unusual move for a Republican. In particular, he has questioned why Floridians saw their rates rise despite the quiet storm season. But Mr. Hartwig said Mr. Crist should not expect homeowners in Florida to benefit from profits the industry reaped in less risky states.

''By law, the price of insurance in each state is based on the experience in that state and that state only,'' Mr. Hartwig said. ''Governor Crist, with all due respect, was basically saying if an insurer earns profits on homeowner policies in Montana or auto policies in Idaho, then somehow that profit should be available to homeowners in Florida to keep their rates down.''

The legislation, approved by votes of 116 to 2 in the House of Representatives and 40 to 0 in the Senate, also repeals an average 21 percent rate increase that took effect this month for customers of Citizens Property Insurance, the state-run corporation, and another average increase of 56 percent that was to take effect in March.

Citizens Property Insurance, which ran substantial deficits in 2004 and 2005, has become the state's largest home insurer, covering 1.3 million households. The new legislation repeals a requirement that it charge higher rates than private companies and allows it to sell more than just windstorm coverage, both changes that rankled private insurers.

Some homeowners said Monday that the changes were not nearly enough given the astronomical rate increases of recent years, and that insurance policyholders should not have to worry about huge assessments in the event of a huge storm.

''It's the pits,'' said Imogene Arnold, 75, who lives in Port Richey and said her Citizens premium climbed to $4,700 from $2,066 in the past year. ''We were really hoping around 40 or 50 percent.''

Representative Susan Bucher, a Democrat from West Palm Beach, said, ''I believe what we did is cosmetic surgery when we need heart surgery.''

Others were resigned, saying that the rate freeze for Citizens customers was at least something positive.

''At least for once the Legislature is listening to consumers and not just the insurance companies,'' said Heather Carruthers, a member of Fair Insurance Rates in Monroe, an advocacy group for policyholders in the Florida Keys. ''I absolutely think it's a good step.''

Asked how she felt about the state's taking on billions of dollars in additional insurance risk, Ms. Carruthers said: ''It's a risk to the economy, but if people move out of Florida, as we've already seen happen, that would be more economically devastating. We have to stop that.''

Mr. Crist, who has offered few of his own ideas for solving the insurance crisis and instead entreated lawmakers to ''get it done,'' described the legislation as a bipartisan victory after it passed Monday.

Lawmakers, for their part, played a recording of ''Kumbaya'' on the Senate floor after voting.

Mr. Hartwig of the Insurance Information Institute said that in the end, lasting insurance relief could come only from building less on Florida's vulnerable coasts and requiring the strictest of building codes, which the recent debate barely addressed.

''You cannot legislate away the real, formidable risk of hurricanes in Florida,'' he said.