How a HELOC Works: The Complete Guide

TL;DR: A HELOC is a revolving credit line secured by your home equity. You borrow as needed during a draw period (typically 10 years) and pay interest only on what you use — at prime plus a margin, so a 1% margin over today’s 6.75% prime means 7.75%. When the draw period ends, the line closes and your payment converts to principal-plus-interest, often jumping 27% to 46% overnight. Understanding that conversion is the single most important part of how a HELOC works.

You’re sitting on more borrowing power than you probably realize. American homeowners hold roughly $11 trillion in tappable equity — the amount they could borrow while still keeping a 20% cushion in their homes, per ICE’s March 2026 Mortgage Monitor. A home equity line of credit is one of the two main tools for accessing it, and it’s the more flexible one. It’s also the more complicated one, because a HELOC changes shape partway through its life.

This guide walks through every mechanical piece: how the two phases work, how the rate gets built, what the payments actually look like in dollars, where the loan sits in your home’s lien stack, and what happens when the whole thing matures.

What is a HELOC, mechanically?

A HELOC (home equity line of credit) is a revolving credit account — the same structure as a credit card — with two differences that change everything: it’s secured by a lien on your house, and it has an expiration date.

Because your home backs the debt, lenders price HELOCs far below unsecured credit. Bankrate’s national lender survey puts the average HELOC rate at 7.43% as of June 2026 — a fraction of typical credit card APRs. The collateral is also why the stakes are higher: fall far enough behind on a HELOC and the lender can foreclose, even if your first mortgage is current.

The “expiration date” part is what trips people up. A credit card revolves forever. A HELOC revolves for a fixed window — the draw period — and then forcibly converts into something that behaves like a conventional installment loan. Two phases, two completely different payment obligations.

How do the draw period and repayment period work?

Every HELOC splits its life into two phases.

The draw period — most commonly 10 years — is the revolving phase. You have a credit limit (say, $100,000), and you can borrow, repay, and re-borrow against it as many times as you want. Lenders typically issue checks, a card, or online transfers tied to the line. Your minimum payment during this phase is usually interest only, calculated on whatever you currently owe — though some lenders require principal-and-interest payments from day one, so confirm the draw-period payment structure before you sign. Owe nothing, pay nothing. Owe $80,000, pay interest on $80,000.

The repayment period — typically 10 to 20 years — begins the day the draw period ends. Three things change at once:

1. The line freezes. You can no longer borrow, even if you have available credit.
2. The payment converts. Your minimum goes from interest-only to fully amortizing — principal plus interest, sized to pay the balance to zero by the end of the term.
3. The clock starts. Whatever you owe on conversion day becomes, functionally, a fixed-term installment loan (usually still at a variable rate).

Here’s the side-by-side:

	Draw period	Repayment period
Typical length	10 years	10–20 years
Can you borrow?	Yes — borrow, repay, re-borrow	No — line is frozen
Minimum payment	Interest-only (usually)	Principal + interest, fully amortizing
Balance trajectory	Flat or growing unless you pay extra	Declining to zero on schedule
Rate type	Variable (prime + margin)	Usually still variable
Monthly cost on $80,000 at 7.75%	~$516.67	~$656.76 (20-yr) / ~$753.02 (15-yr)

That last row is the headline. We’ll build those numbers from scratch in a minute.

One wrinkle worth knowing: not every HELOC follows this template. A minority are structured with a balloon maturity instead — the entire balance comes due at the end of the draw period with no built-in repayment phase. More on that in the maturity section, because it’s the difference between a payment increase and a six-figure bill.

How is a HELOC rate set? Prime plus margin

Nearly every HELOC in the U.S. prices off the same formula:

Your rate = WSJ Prime Rate + your margin

Prime is a benchmark rate that major banks publish, currently 6.75%, effective December 11, 2025, per JPMorganChase’s historical prime rate record. Prime isn’t arbitrary — it tracks the Federal Reserve’s federal funds rate almost mechanically, sitting 3 percentage points above the top of the Fed’s target range. The Fed held that range at 3.50%–3.75% at its April 28–29, 2026 meeting, which is why prime has been parked at 6.75% since December. (3.75% + 3.00% = 6.75%. The math is that literal.)

Your margin is the lender’s adjustment for your specific file — credit score, combined loan-to-value, documentation — fixed at closing for the life of the line. Strong borrowers can see margins at or even below zero (lenders currently advertise introductory and discounted pricing for top-tier credit profiles); weaker files or higher CLTVs get wider margins. The June 2026 Bankrate average of 7.43% sits 0.68 points over prime, which tells you roughly where the middle of the market’s margins land. What lenders are advertising this week moves constantly — our current HELOC rates page tracks it.

Two consequences of this structure matter more than anything a rate sheet shows you:

1. Your rate is a moving target. When the Fed cuts or hikes, prime follows within days, and your HELOC rate resets — usually the next billing cycle. You don’t get a say. The next scheduled FOMC meeting is June 16–17, 2026; every one of the eight meetings a year is a date your payment could change.

2. The margin is forever, the promo isn’t. Lenders frequently advertise low introductory rates for the first 6–12 months. The number that determines your cost for the next 20–30 years is the post-promo margin. When you compare offers, compare margins.

Most HELOCs also carry rate caps — a lifetime maximum (and sometimes a floor) written into the agreement. Read yours; caps vary widely by lender and state.

The worked example: $80,000 at prime + 1%

Numbers make this concrete. Say you’ve drawn $80,000 against your line, your margin is 1%, and prime is 6.75%. Your rate: 7.75%. (Close to the 7.43% national average — this is a realistic middle-of-market scenario, not a best case or worst case.)

Draw-period payment (interest-only)

Interest-only math is simple: balance × rate ÷ 12.

$80,000 × 7.75% = $6,200 per year ÷ 12 = $516.67 per month

That’s your minimum. Pay it every month for the entire 10-year draw period and here’s your scorecard:

• Total paid: $62,000
• Principal reduced: $0
• Balance at end of draw period: $80,000 — exactly where you started

That’s not a flaw; it’s the design. Interest-only minimums are why HELOC payments look so light next to other debt. But the design only works in your favor if you understand that the minimum payment is a treadmill, not a staircase.

Because the rate floats, so does that payment. If the Fed cuts a quarter point and prime drops to 6.50%, your rate becomes 7.50% and the payment falls to $500.00. If prime instead rises half a point to 7.25%, your rate is 8.25% and the payment climbs to $550.00. Same balance, three different payments — that’s variable-rate life. (Handy rule of thumb at 7.75%: every $10,000 of balance costs about $64.58 a month in interest.)

Repayment-period payment (amortizing)

The day your draw period ends with that $80,000 still outstanding, the lender re-casts it as an amortizing loan. Using a standard amortization formula at the same 7.75%:

• 20-year repayment term: $656.76/month
• 15-year repayment term: $753.02/month

The payment-shock math

	Interest-only (draw)	20-yr repayment	15-yr repayment
Monthly payment	$516.67	$656.76	$753.02
Increase	—	+$140.09 (+27%)	+$236.35 (+46%)

A 27% to 46% jump in a required monthly payment, on a date set ten years in advance, is what the industry calls payment shock — and it’s the single most common way HELOCs hurt people. The borrowers who get burned aren’t the ones who didn’t understand interest rates; they’re the ones who budgeted around the $517 minimum for a decade and forgot the conversion was coming.

The full lifecycle cost is worth staring at, too. Ride the minimums the whole way — 10 years of interest-only, then 20 years of amortization — and the $80,000 draw costs $62,000 in draw-period interest plus $157,622 in repayment-period payments: $139,622 of total interest on $80,000 borrowed, assuming the rate never moves (it will). Voluntarily paying principal during the draw period collapses that number, which is why it’s the standard advice for anyone carrying a long-term HELOC balance.

Run your own balance, margin, and term through our HELOC payment calculator — the shock math changes a lot depending on how much of the line you actually use.

Why does the credit-line structure matter vs. an installment loan?

The revolving structure is the entire reason to choose a HELOC over its sibling, the home equity loan (a lump-sum, fixed-rate installment loan). Three practical differences:

You pay interest only on what you’ve drawn. A $100,000 HELOC with a $20,000 balance charges interest on $20,000. A $100,000 home equity loan charges interest on $100,000 from day one, whether you needed it all immediately or not. For staged expenses — a phased renovation, tuition due each semester, a standby emergency fund — the line structure can save you years of interest on money you weren’t using yet.

Repaid principal comes back. Draw $30,000, pay it back in year two, and you have $30,000 of capacity again — no new application, no new closing costs. An installment loan’s repaid principal is just gone; borrowing again means originating again.

Flexibility cuts both ways. The installment loan’s rigidity — fixed rate, fixed payment, forced principal reduction from month one — is a feature if you want the debt on a guaranteed path to zero. The HELOC’s interest-only minimum and open spigot demand more discipline. Neither is “better”; they’re built for different jobs. The full breakdown lives in our HELOC vs. home equity loan comparison, and the most common ways borrowers deploy each are covered in what people use home equity for.

What does “second-lien position” actually mean?

When you close a HELOC while still carrying a regular mortgage, the HELOC lender records a lien against your home behind the mortgage lender’s lien. That’s second-lien (or “junior”) position, and it drives more of the HELOC’s economics than most borrowers realize.

For the lender, second position is structurally riskier. If the home is ever foreclosed and sold, the first-mortgage lender gets paid in full before the HELOC lender sees a dollar. If the sale proceeds run out, the second lien eats the loss. That risk shows up in your pricing: the average HELOC at 7.43% runs about 0.91 points above the 6.52% average 30-year fixed mortgage (Freddie Mac PMMS, week of June 11, 2026). You’re not paying more because the money is different — you’re paying for the lender’s spot in line.

For you, three things follow:

1. Combined loan-to-value (CLTV) caps your line. Lenders size a HELOC against your first mortgage balance plus the new line, typically capping the combined total at a percentage of your home’s value (80–90% is the common range, varying by lender and profile). Estimate your available equity with our home equity calculator, and see the full underwriting picture — credit, income, CLTV — in our HELOC qualification guide.

2. Default on either loan endangers the house. A second-lien holder can initiate foreclosure on its own. It’s economically unattractive for them unless there’s enough equity to cover both liens, but the legal right exists. A HELOC is not “softer” debt because it’s second in line.

3. Subordination becomes your problem later. If you refinance your first mortgage while the HELOC is open, the new first lender will require the HELOC lender to sign a subordination agreement — formally agreeing to stay in second position behind the new loan. Most HELOC lenders cooperate, but it adds time, sometimes a fee, and occasionally a refusal that forces you to close the line to complete the refi.

One more case: if your first mortgage is paid off, your HELOC records in first position. Some lenders price first-lien HELOCs more aggressively for exactly the reason above — they’re first in line now.

Can you fix the rate on a HELOC?

Increasingly, yes — without giving up the line. Many lenders now offer a fixed-rate conversion option (marketed as a “fixed-rate lock,” “fixed-rate advance,” or similar): you carve a chunk of your variable balance into a fixed-rate, fixed-payment, fixed-term sub-loan inside the HELOC.

Typical mechanics, which vary by lender:

• Minimum lock amounts (often $5,000–$10,000 per lock)
• A cap on simultaneous locks (commonly two or three at a time)
• A modest rate premium over your current variable rate — you’re buying certainty
• Term choices for the locked portion, e.g., 5, 10, 15, or 20 years, with amortizing payments
• Unlock/re-lock provisions, sometimes with a fee

The strategic use case: borrow flexibly at the variable rate during a project, then lock the final balance once spending stops — converting rate risk to a predictable payment while keeping the rest of the line open for the future. Whether locking beats staying variable depends on where rates head next, which is exactly the thing nobody can promise you. What you can do is compare the lock premium against your own tolerance for payment swings.

A few lenders also offer the inverse product — a HELOC that’s fixed-rate by default — and standalone home equity loans remain the purpose-built fixed-rate option; see the comparison for when each structure wins.

What happens when a HELOC matures?

“Maturity” gets used loosely with HELOCs, so split it into the two events that matter: the end of the draw period and the final maturity date of the whole agreement.

At end of draw, one of three things happens, depending on your contract:

1. Automatic conversion to amortization (most common). The balance converts to the repayment-period schedule — the $516.67 → $656.76 math above. No action required, but the payment jump is mandatory.

2. Renewal. Some lenders — banks and credit unions especially — will review your file near end-of-draw and offer to renew or re-originate the line, restarting a fresh draw period. This is underwriting-contingent: they’ll re-check credit, income, and home value. A renewal that looked automatic when you opened the line can evaporate if your finances or the housing market deteriorated. Lenders also retain the right, in most agreements, to freeze or reduce a line mid-draw if your home’s value drops significantly or your financial circumstances change materially — a clause exercised widely during 2008–2009.

3. Balloon maturity. Less common in today’s market but still written: the full outstanding balance is due when the draw period ends. On our example, that’s an $80,000 bill on a single date. If you hold a balloon-structured line, your realistic endgame is refinancing it before maturity — into a new HELOC, a home equity loan, or a first-mortgage refinance.

Your practical options as the date approaches (start 12–18 months out):

• Ride the amortization. Budget for the converted payment and let the schedule pay the debt off. Cheapest in fees; requires absorbing the payment jump.
• Renew with your lender or open a new HELOC elsewhere and roll the balance — restarting interest-only flexibility, and restarting the clock on eventually repaying principal.
• Refinance into a home equity loan for a fixed rate and a forced payoff path.
• Roll it into a first-mortgage refinance — consolidating both liens into one new mortgage. The math depends heavily on the spread between your existing first-mortgage rate and current refi pricing; with 30-year money averaging 6.52% and HELOCs averaging 7.43%, the answer is different for someone holding a 3% pandemic-era mortgage than for someone at 7%.
• Pay it down aggressively before conversion, shrinking the balance the amortizing payment gets calculated on.

Which path fits depends on your balance, your first mortgage, and where rates sit at the time — model your scenarios with the payment calculator rather than guessing.

The mental model to keep

Strip away the details and a HELOC is this: a 10-year option on cheap, flexible borrowing, attached to a 10-to-20-year installment loan that activates automatically on whatever you still owe. The first half is genuinely one of the most flexible, lowest-cost borrowing tools a homeowner can hold. The second half is a conventional debt with a payment 27–46% higher than the one you got used to.

Borrowers who treat the draw-period minimum as the real cost of the money get surprised. Borrowers who plan around the conversion date — paying principal early, locking rates when it makes sense, or refinancing on their own schedule instead of the lender’s — get the flexibility without the shock. The difference between the two isn’t financial sophistication. It’s knowing the conversion is coming, which, as of right now, you do.