Home equity line of credit rates to rise; here's what to do.

Mortgage rates may be a mystery; they move up one day and down the next, often befuddling the experts. However, the prime rate, which is the foundation for the interest you’re charged on home equity lines of credit, is a bit more transparent.

The Federal Reserve establishes short-term rates — and indirectly the prime rate — in an effort to reach economic targets. When the Fed raises rates, mortgage rates may or may not respond immediately, but the prime rate reacts right away. With one increase in each of the past two Decembers, and with a Fed plan to raise rates three more times this year, it’s pretty clear: Your HELOC rate is likely heading higher.

Primed for higher rates

“HELOC loans are generally a function of prime plus something,” says Brian Sacks, branch manager of HomeBridge Financial Services in Pikesville, Maryland. That “something” is a margin, a set markup that varies by lender. For example, if the prime rate is 3.75% and a lender adds a margin of 2 percentage points, your HELOC interest rate would be 5.75%.

“Prime will likely go up several times in the coming year,” Sacks says. “And certainly, long term, prime is likely to continue to rise.”

He says we’ve likely hit the “low end of the interest rate cycle for quite some time.”

If you’re going to be staying in the same home for more than the next two to three years, Sacks says you should seriously consider refinancing your home equity line of credit into a fixed-rate loan.

Big balance? Beware but don’t panic

“It’s still relatively inexpensive to borrow,” says Sean Andrews, senior manager for consumer credit products with KeyBank in Cleveland. He says traditional second-mortgage HELOC borrowers, who have tapped their home equity in a line of credit for home improvements and the like, still have quite a bit of headroom before higher rates start encouraging a change in plan.

However, for those homeowners who have a substantial balance, it might soon be time to seek a fixed-rate option, he adds. In that case, keep an eye on the prime rate.

For those with first-lien HELOCs

Over the past few years, as the prime rate remained in the cellar, Andrews says some borrowers began using HELOCs to refinance their primary, or first-lien, mortgage. First lien means the loan is first in line from a collection standpoint — the highest priority debt placed on a property.

One reason borrowers used a HELOC instead of a typical purchase mortgage: HELOCs often don’t have closing costs, he says, though some lenders will require you to pay an annual fee or origination charge.

Refinancing into a HELOC with no closings costs has been very attractive to homeowners, particularly those who didn’t plan on being in their home long term. Now, as rates start moving higher, Andrews says some customers have already begun moving those first-lien HELOCs to fixed-rate loans.

The case for a HELOC conversion

Dodging higher interest rates doesn’t mean you have to give up your home equity line of credit. Many banks let customers take a portion of their variable-rate line and convert it to a fixed-rate loan.

“It’s taking a chunk of your line and fixing [the rate] so that you can protect yourself from future rate movements,” Andrews says. You still have the remaining available line of credit to draw on as you desire, with variable-rate interest charged only when the proceeds are drawn.

The cost of waiting

While it may be human nature to put such decisions on hold for a while, waiting to consider your options for too long can get you stuck on a ramp of rising interest rates.

Rates could have a “significant and consistent pattern of going up,” thus rendering a HELOC unaffordable, Sacks says. Even if your HELOC has a lifetime rate cap that limits how high your interest can rise, it may be a good time to shop options, he says.

“If nothing else, it’s worth exploring the opportunity of refinancing,” by perhaps combining your first and your second mortgage in a refinance.

“During these moments in time, when rates actually thaw and start moving, customers should unpack their agreements,” Andrews says. By dusting off and reviewing those loan docs now, you might prevent the potential impact of procrastination.

If you wait to fix your rate until after interest rates have made a significant move higher — “I want to be honest with you, at that moment, it’s too late.”

Hal Bundrick is a staff writer at NerdWallet, a personal finance website. Email: hal@nerdwallet.com. Twitter: @halmbundrick.

This story originally appeared on NerdWallet.