MINNEAPOLIS — This year is likely to be a little cheerier at Kevin Coughlin’s home. Coughlin refinanced the adjustable-rate mortgage on his Shorewood, Minn., house last month into a 30-year fixed-rate mortgage that’s going to save him $200 a month.

“It takes the pressure off the cash flow,” he said, speculating about how he and his family might benefit from the savings. “Whether it’s groceries or the ability to eat out one more time each month — before, you weren’t going to do it.”

Nationally, mortgage rates fell to an average of 5.1 percent last week, the lowest level in nearly four decades, according to a weekly survey by Freddie Mac. Some lenders were reporting even lower rates, and area mortgage lenders say applications are pouring in.

It’s too soon to say what effect the rates will have on the moribund real estate market. The most immediate beneficiaries appear to be homeowners hoping to swap their adjustable-rate mortgages for fixed payments.

“This is nearly a historical and probably unprecedented opportunity,” said Keith Gumbinger of HSH Associates, a financial publisher in New Jersey.

Not everyone will be able to latch on to the lower rates. Homeowners whose property values have fallen may not have enough equity to qualify for the lower rates, and lenders are scrutinizing applications more closely now than during housing’s go-go years earlier this decade.

The decline in mortgage rates comes after aggressive moves by the Federal Reserve aimed at propping up the U.S. housing market. On Dec. 16, the Federal Open Market Committee lowered a key interest rate, and in November the Fed said it would buy $600 billion in mortgage-related securities and other debt issued by Fannie Mae, Freddie Mac and the Federal Home Loan banks.

The latest rate decline is unlikely to revive the ailing housing market. According to a survey by the Mortgage Bankers Association last month, refinancings represented almost 77 percent of all mortgage applications.

Buying a house is a much more complicated process than simply refinancing, and many prospective borrowers aren’t feeling confident enough about the economy to make a big financial commitment, said Ken Johnson, vice president of the Coldwell Banker Burnet office in Minnetonka, Minn.