(Bloomberg) -- U.S. catastrophe reinsurance rates may rise about 15 percent next month after the financial crisis eroded insurers’ capital and as the market for catastrophe bonds to offset potential hurricane losses remains limited, insurance broker Aon Corp. and reinsurers including Munich Re said.

“Since the damage frequency of hurricanes has increased and the security of reinsurers becomes increasingly important, the prices have to be adapted,” Anke Rosumek, a spokeswoman for Munich Re, said in a telephone interview on June 4.

Insurers worldwide have written down almost $243 billion on investment losses related to the financial crisis since it began in 2007. Primary insurers can use so-called cat bonds to replace traditional reinsurance to protect against some of the largest or least likely losses, including hurricanes. The market for cat bonds was brought to a standstill last year after the collapse of Lehman Brothers Holdings Inc.

Billionaire Warren Buffett, chairman of Berkshire Hathaway Inc., has scaled back coverage of hurricanes at insurance units, he said May 2 at Berkshire’s annual meeting in Omaha, Nebraska.

“We are doing less natural risk in terms of hurricanes because we have plenty of capital but we don’t have as much excess capital as we had a couple years ago. So we cut back somewhat on the insurance risk we take,” he said.

Hurricane reinsurance rates, which are currently being renegotiated, may rise by about 20 percent this summer, Torsten Jeworrek, management board member responsible for reinsurance at Munich Re, the world’s largest reinsurer, said at a conference in Cologne last month.

Combined Ratio

Hannover Re, Germany’s second-biggest reinsurer, expects to raise rates, though spokesman Stefan Schulz declined to give an estimate of the increase ahead of next month’s contract negotiations.

Josephine Chennell, Zurich-based spokeswoman for Swiss Reinsurance Co., the world’s second-largest reinsurer, declined to comment on U.S. premiums.

Swiss Re’s combined ratio, or claims compared with premium income, increased to 99.8 percent in the three months to Sept. 30, from 82.5 percent in the same period the year before, amid higher natural catastrophe claims from hurricanes Gustav and Ike. A ratio above 100 indicates an underwriting loss.

“Florida-influenced reinsurance programs renewing at June 1 have an estimated year-on-year rate increase of around 10 to 15 percent,” Bryon Erhart, chief executive officer of Aon Benfield Analytics, said in a telephone interview from Chicago on June 5. The increase is “good news” for reinsurers because the price per unit of risk has advanced, he said.

Reinsurers’ Profit

“Reinsurers should be able to take advantage of this increasing profitability,” said Roland Pfaender, a Frankfurt- based analyst at Commerzbank AG.

The increase may raise consensus earnings-per-share estimates from 2010 onwards, said Brian Shea, a London-based analyst with Bank of America Merrill Lynch Research, in a note on June 5.

U.S. property and casualty insurers paid an estimated $26 billion in catastrophe-related losses in 2008, according to the Insurance Service Office, a New Jersey-based supplier of actuarial data. Overall, catastrophe losses added 5.2 points to the industry’s statutory combined ratio in 2008, compared with just 1.5 points during 2007. Hurricane Ike caused about $20 billion in insured damages last year, according to Swiss Re, making it the third most expensive hurricane ever.

“Few new sources of capital have emerged thus far in 2009,” Aon said in its report on catastrophe reinsurance renewals covering Florida at June 1. Still, Erhart said this year’s comeback of catastrophe bonds, the investments that pay out as long as there are no major hurricanes or earthquakes, is a “positive sign” that the market might improve. “The capacity for catastrophe bonds is rebuilding itself,” he said.

The hurricane season, which started on June 1 and lasts until November 30, will be “near-normal,” the National Oceanic and Atmospheric Administration said last month. It expects four to seven hurricanes forming in the Atlantic.