How HELOCs actually work:
the rate, the shock, and the math that saves you.

A HELOC looks simple on the disclosure: a rate, a limit, a thirty-year life. Underneath, three things control what it actually costs you. The Fed sets the rate, which can move at every meeting. Your choices during the first ten years determine how much principal you pay down. And what happens on the day the draw period ends decides whether the loan stays manageable or doubles the monthly bill. This page covers all three: how the rate is built, how the payment changes, what the year-10 jump looks like in dollars, and what you can do now to soften it.

The two chapters of a HELOC

A HELOC is two loans in sequence, separated by a moment called the end of draw.

During the draw period — the first 10 years, though a handful of lenders (Navy Federal) offer 20 and some aggressive ones offer 5 — you can borrow from your approved line as often as you want, pay it back, and borrow again. It works like a credit card, secured by your house. Your minimum payment each month is usually just the interest on whatever balance you're carrying. On a $60,000 balance at 7.02%, that's about $357 a month. Interest-only means none of that $357 reduces the $60,000 principal. The balance at the start of month one and the balance at the start of month 120 are identical.

During the repayment period, the line closes to new borrowing. Whatever balance you're carrying becomes a regular installment loan, paid down over 10 to 20 more years at the same variable rate. Your payment now includes principal and interest. On the same $60,000 balance at 7.02% over a 10-year repayment, the new minimum payment is about $700 a month, nearly double the draw-period payment. The jump happens on the first bill of the new period, not gradually.

A small share of HELOCs skip the repayment period and require a balloon payment: the full balance due on the day the draw period ends. Regions Bank offers the most widely known example. Balloon HELOCs are non-qualified mortgages, meaning the lender is not required to verify you can repay. If your loan has a balloon, it will be in the closing paperwork. Look for the word.

How the rate is actually built

The rate on your HELOC bill is a formula, and every part of it matters.

The base is the U.S. Prime Rate, the benchmark most consumer loans track. Prime sits, by convention, exactly 3 percentage points above the Federal Reserve's target rate, so when the Fed raises or cuts rates at a meeting, Prime moves the same amount within a day. As of April 2026, Prime is 6.75%, down 1.75 points from its 8.50% peak after seven cuts between September 2024 and December 2025.

On top of Prime, your lender adds a margin: a markup between 1 and 5 percentage points, set at closing and fixed for the life of the loan. The margin is priced off your credit score, your equity, and your overall risk profile. Equity is measured as combined loan-to-value: the total of your first mortgage plus your HELOC divided by your home's value. A borrower with a 780 credit score and 60% combined loan-to-value might get Prime + 1.25% (an 8.00% rate). A borrower with a 680 score and 85% combined loan-to-value might get Prime + 4.50% (an 11.25% rate). Same Prime, very different bills.

Once that formula is set at closing, two rules govern how much the rate can move:

• Lifetime cap. Federal law requires one. It is almost always 18%, high enough that most borrowers think of it as a theoretical ceiling. During the tightening cycle of 2022–2023, borrowers with margins above 4% did hit it.
• Periodic cap. A periodic cap limits how much your rate can move between adjustments, for example, no more than 2 percentage points per year. Most HELOCs do not have one. Your rate can rise a full point in a single month, and your next statement reflects the change. An adjustable-rate first mortgage, by contrast, is typically capped at 2 points per year and 5 points over the life of the loan. A HELOC has no such cushion.

The practical point: the rate at closing is not the rate on your next bill. When the Fed moves, your payment moves, often within one billing cycle. That is what “variable rate” actually means.

The math, for a $60,000 HELOC

Here is what the draw-to-repayment transition looks like on a typical $60,000 HELOC at April 2026's 7.02% average rate: first the path most borrowers take, then two versions of the disciplined path.

The gap between the top row and the middle row is the cost of treating the draw period as free money. The gap between the top row and the bottom row is the cost of treating a HELOC as a 20-year loan instead of a 10-year one. The $357-a-month interest-only option is a real monthly savings, but it's a delay, not a saving. At the end of the delay, you still owe the original $60,000 and your payment almost doubles.

The interest-only HELOC costs $42,720 more in total interest than the HELOC you pay off during the draw period. That gap is the price of the flexibility. For some borrowers the flexibility is worth the price. For most it isn't, because most borrowers don't end up using the flexibility. They just use the smaller monthly payment.

What happens when rates move

The math above assumed the rate stayed at 7.02% for twenty years, which is not what happens in real life. Between January 2022 and August 2023, during the Fed's most recent tightening cycle, Prime went from 3.25% to 8.50%, more than five percentage points in eighteen months. Any HELOC taken out in early 2022 more than doubled in cost before 2023 ended.

Here's the same $60,000 interest-only HELOC under three rate paths:

For context: a fixed-rate home equity loan at 10 years and 7.59% (current April 2026 averages) on the same $60,000 balance costs about $25,620 in total interest. The interest-only HELOC at today's rate costs ~$66,840. Under a four-point rate rise, it costs $108,000, nearly four times the fixed home equity loan. And the total doesn't capture the cash-flow hit: the monthly payment during the draw period roughly doubles, which is often enough to break a budget.

The numbers above are a stress test, not a prediction. A borrower shopping for a HELOC should ask two questions before signing: Can I afford the payment at Prime + 4%? and Can I afford the first repayment bill at that same rate? If the answer to either is no, the HELOC is too much loan. The disciplined-path math doesn't save you either, because the disciplined path carries the same rate risk.

The risk of a HELOC is not mainly that the rate might move. The risk is that the payment structure asks you to manage your own principal paydown for ten years, then doubles the minimum payment in month 121 if you haven't.

Four surprises most borrowers miss

Beyond the rate and the payment jump, four things catch borrowers late. Each is in the contract, but not in the sales pitch.

1. Most HELOCs have no monthly cap on how much the rate can move

A standard adjustable-rate first mortgage is typically capped at 2 percentage points per year and 5 over the life of the loan. Most HELOCs have only the 18% lifetime ceiling. Between adjustments, which usually happen monthly, the rate tracks Prime. If the Fed moves a full percentage point in a single month, your rate moves a full percentage point in a single month. Planning around “a percent or two over the next few years” is planning around an average, not the contract.

2. The lender can freeze your line

Under federal consumer-protection rules, a HELOC lender can suspend your ability to draw when any of a handful of triggers hits: a meaningful drop in your home's value, a serious hit to your finances, or the lender deciding you can no longer cover the payments. That is what happened during the 2008 crisis. Countrywide froze an estimated 122,000 HELOCs; USAA reduced or froze roughly 15,000 more; Bank of America, Chase, Citibank, Washington Mutual, Wells Fargo, National City, and IndyMac all followed. A CNN Money story from April 2008 described a homeowner whose HELOC was canceled because her credit score had dropped. She found out when she tried to use the line.

It isn't only history. Jeff Taylor of the Mortgage Bankers Association recently told CBS News: “If you take out a HELOC and your home value decreases materially, your lender could notify you that they intend to freeze your ability to draw on your HELOC.” As of Q1 2026, national listing prices are down 2.2% year over year, with some metros off 7%. The rules are written for exactly that environment.

3. Refinancing your first mortgage later gets complicated

If you take out a HELOC and later decide to refinance your first mortgage, to capture a lower rate, pull cash out, or change loan types, your HELOC lender has to agree to stay in the second-lien position behind the new first mortgage. That agreement is called subordination, and the HELOC lender can refuse. The process takes two to four weeks and costs about $250 in fees. Approval is routine when your combined loan-to-value stays below 85%, but lenders balk when credit has dropped, income has softened, or the new first-mortgage amount pushes total leverage up. A refusal can force you to pay off the HELOC in full just to close the refinance.

4. A small share of HELOCs have balloon payments

Most HELOCs convert to a repayment period at year 10. Some instead require the full outstanding balance to be paid on a specific date, typically the day the draw period ends. Regions Bank is the most widely offered example. A balloon HELOC falls outside the federal rules that require lenders to verify you can afford to pay the loan back. If you can't pay the balloon when it comes due and you can't refinance into another loan, the lender's next step is foreclosure. Read the repayment terms before closing. Lenders do not put the word “balloon” on the first page.

Three ways to defuse payment shock

The payment jump at year 10 is not inevitable. There are three moves a borrower can make. The first is the cheapest. The other two cost money, but they are real options when the first one is not available.

The cheapest move: pay principal during the draw

Nothing in the HELOC contract says you have to pay only the interest-only minimum. Most lenders accept voluntary principal payments with no fee. The scenarios above assumed either $357/month (the minimum) or the full P+I payment ($470 or $701). You don't have to go that far. Even an extra $100/month toward principal during a 10-year draw period shrinks the eventual repayment-period payment meaningfully. Every dollar of principal you pay during the draw is a dollar that isn't still there when the payment resets at month 121.

The hedge: lock part of the balance to a fixed sub-rate

Many HELOC lenders (U.S. Bank, PNC, Bank of America, BMO, most credit unions) let you convert part of your outstanding balance into a fixed-rate sub-loan inside the HELOC, usually for a term of 5 to 30 years. The locked portion comes out of your variable-rate balance and pays itself off on its own fixed schedule. You pay for the certainty: the fixed rate is typically 0.5 to 1.5 percentage points above the variable rate. Some lenders (U.S. Bank) waive the conversion fee; others (PNC) charge around $100 per lock. If you expect rates to rise and cannot pay down fast enough to get ahead of the rise, locking is the hedge.

The exit: refinance before the shock

The third option is to leave the HELOC before the payment structure changes: either into a new HELOC (which restarts a fresh draw period), into a fixed home equity loan (which locks the rate and payment), or into a cash-out refinance rolled into the first mortgage (which only makes sense if the new blended rate beats your current first-mortgage rate). Each path involves closing costs, and each takes time. The time to start thinking about the refinance is month 96, not month 119, when you still have a year to shop, compare, and choose.

When to just pay it off

Sometimes no strategy makes a HELOC the right tool. The right move then is to stop drawing and close the line, rather than keep a second mortgage hanging over the house. A few situations where that call is usually the right one:

• Your income is unstable. Both the draw-period and repayment-period payments assume a household that can write the check every month for a decade. If a layoff, a medical event, or a business slowdown would make either number hard, a frozen line doesn't solve the problem, and neither do the strategies above.
• Your home's value has fallen near or below the approved line. Federal rules allow lenders to freeze lines in that environment, which means the “emergency fund” aspect of the HELOC is gone exactly when you would want it. Retire the balance and stop paying the annual fee.
• You are within a few years of retirement. A variable-rate loan secured by your home is a poor match for a fixed, reduced income. If the HELOC was meant to finance something that still matters after retirement, consider refinancing to a fixed home equity loan before the income change.
• The original need is over. People draw HELOCs for a specific job: a renovation, a business launch, a bridge between homes. When the job is done, leaving the line open indefinitely trades an open door for a small annual fee and the risk of being frozen in a bad market.
• The numbers don't work. Paying Prime + 4% on a non-essential project while carrying higher-rate debt elsewhere (credit cards, student loans) is backwards. Pay down the higher-rate debt first.

The decision, in one paragraph

A HELOC is a product with a specific shape: flexible and cheap in the first ten years, structured and expensive in the next ten, variable-rate throughout. On a $60,000 balance, the borrower who treats the interest-only minimum as the real cost pays roughly forty thousand dollars more than the borrower who pays the line down during the draw. The cheapest way to use a HELOC is to pay it like a home equity loan. The most expensive is to let it run to year 10 without a plan. Before signing, stress-test the payment against Prime + 4% in both the draw and repayment periods. If the answers hold, the product is as useful as it's advertised to be. If they don't, the borrowing is a bet on your future self's income.