Homeowners across the country -- especially those with adjustable-rate mortgages in the upper 10 percent range and beyond -- are ringing in the new year with a rush to money-saving refinancings.

The most popular loan switches, according to analysts who monitor more than 2,000 local lenders nationwide, are from one-year adjustables to medium-term fixed-rate balloon and convertible mortgages in the upper 8 percent and lower 9 percent ranges.

That's the word from Keith Gumbinger, vice president of HSH Associates, the largest mortgage rate-tracking firm in the United States.

"I think people see the chance to cut their monthly payments, and they probably also see a limited time period to make the move," said Gumbinger in an interview last week. "Who knows what happens to rates if shooting starts {in the Persian Gulf}?"

Fixed rates for mortgage money at all maturities hit three-year lows last week. Conventional 30-year money went for an average 9.7 percent (plus 2.2 points) nationally. Fifteen-year fixed-rate loan quotes averaged 9.4 percent plus 2.1 points. (A point equals 1 percent of the loan amount.)

But the most enticing fixed rates in many markets were in the five-year and seven-year balloons, "two-steps" and similar mid-range loan products. Balloon loans require full repayment at some specified date. Two-steps are balloons that allow automatic refinancing to a fixed rate for an additional period of years, usually 23 or 25.

Rates in large, competitive metropolitan markets dipped well below the 9 percent mark for borrowers willing to take a fixed rate for 60 to 84 months. The principal rate-monitoring service for the D.C. area, Peeke Loanfax, reported rates of 8.5 plus 1.25 points for some five-year fixed-rate, two-step mortgages. Other lenders offered seven-year fixed-rate balloons at 8.75 percent with two to three points.

Given the opportunity for a possible refinancing to single-digit rates early in 1991, how do you know whether to take the plunge? Here are some quick guidelines for the current marketplace:

If your objective is simply to lower your rate by a "refi," you'll find the windows at virtually all lenders wide open. But if you want to "cash out" additional money -- increase the debt on your home and pocket some tax-free cash to boot -- you'll find fewer windows at the same rate.

Cash-outs used to be treated like ordinary refinancings at most lending institutions. But in an era of soft or declining home values, many lenders now don't want to take the risk. At the very least, be ready for higher rate quotes on cash-outs. And if your property is an "investor" rental home or condominium, good luck. Lenders may not want to know you at any price.

If your loan is in the "jumbo" category (above $191,250), figure on getting refi quotes one-half a percentage point or more above those on smaller "conforming" mortgages. Jumbo loans create jumbo risks, lenders insist, and borrowers have to pay for those worries.

Don't be mesmerized by the lending industry's mortgage mantra: "Don't refinance unless you can cut your rate by 2 percentage points." Though the rule has the merit of simplicity, slavish adherence to it can cost you thousands of dollars.

Instead, try this: Figure the costs of refinancing your current loan using actual loan alternatives available in your market. Then see how long it will take you to save enough on lower monthly payments to "pay" for those costs. Even if your rate change is just 1.25 or 1.5 percent, you may find that your payment savings allow you to recoup your refi expenses in shorter order than you would imagine.

Consider this example prepared by David Ginsburg, president of the mortgage analysis service, Loantech Inc. in Gaithersburg. Say you have an existing mortgage of $229,500 on your house at 11.25 percent. You're in the 33 percent federal tax bracket and you plan to live in the same house for the foreseeable future. You find numerous fixed-rate loans available in the market today at 9.75 percent. Should you wait for rates to hit 9.25 percent, which may be the financial equivalent of waiting for Godot?

Your principal and interest monthly payment on a $229,285 new loan at the 9.75 percent rate will drop to $1,970 from your current $2,229. That's a $259 saving every 30 days, $18,658 over the coming six years. But your refi costs will be substantial: $4,586 in loan points and $1,000 for closing expenses. You also lose out on a certain amount of federal tax write-offs by switching to the lower rate. But you do get to write off $1,513 on your loan points.

How does it all net out? You break even on the deal in just 23 months. That is, your monthly savings pay your transaction costs in less than two years. In 72 months, your net savings come to $8,428. Not a bad move, it turns out, even if you had to break the lenders' golden rule of refinancing to do it.