For a HELOC tied to prime, a quarter-percentage-point increase adds about $20.83 a month in interest on a constant $100,000 balance. The same move adds about $10.42 on $50,000 or $41.67 on $200,000. Those figures describe interest alone, using an annual-rate-divided-by-12 illustration; the amount due under a particular agreement can be different.
RateZip's home-equity dashboard recorded a 7.00% bank prime rate as of October 1, 2026, sourced from the Federal Reserve series carried by FRED. Prime is an index, not a HELOC quote. A line priced at prime plus one percentage point would have an 8.00% interest rate in that example, before considering its specific contract provisions.
| Constant balance | Added monthly interest after +0.25 percentage point | After +0.50 percentage point | After +1.00 percentage point |
|---|---|---|---|
| $50,000 | $10.42 | $20.83 | $41.67 |
| $100,000 | $20.83 | $41.67 | $83.33 |
| $200,000 | $41.67 | $83.33 | $166.67 |
Hypothetical arithmetic: balance × annual rate change ÷ 12. Balances are held constant. Actual interest can use daily accrual; principal payments, fees, floors, caps and adjustment dates can change the bill.
The contract connects prime to the payment
A headline about the Federal Reserve does not establish the timing or size of a borrower's next payment change. The agreement identifies the index, margin, reset timing, any introductory terms and any rate limits. It also determines whether a payment is interest-only during a draw period or includes principal. A later repayment period can change the payment even if the interest rate stays flat.
U.S. Bank's explanation of home-equity borrowing distinguishes a variable-rate HELOC from a fixed-rate home-equity loan, and describes fixed-rate options for eligible HELOC balances. Such an option changes the treatment of the converted balance, not necessarily the entire line.
A fixed-rate alternative changes more than rate risk
For a concrete advertised comparison, U.S. Bank's home-equity loan page showed a 7.65% APR example dated October 1, 2026: a 10-year second-lien loan in the $50,000–$99,999 range with loan-to-value of 60% or less. The advertised example requires a FICO score of at least 730; automatic payments from a U.S. Bank personal checking or savings account are required for the lowest advertised rate. Rates may vary by region, loan-to-value, credit score and loan amount. Approval is subject to credit approval, and the lender excludes trust-held properties in Hawaii, Louisiana, New York, Oklahoma and Rhode Island. This is a dated lender example, not an offer to the reader or evidence that a fixed loan is universally cheaper.
A fixed loan generally amortizes a lump sum over its term. Comparing that payment with interest alone on a HELOC would understate the difference in repayment obligations. Compare the same borrowed amount, fees and repayment horizon, then separately evaluate how much future rate variation the household can absorb. The table above measures sensitivity; it does not predict a Federal Reserve decision.
RateZip is operated by Peklava LLC, DBA RateZip, a licensed mortgage broker (NMLS ID 1592292). We are compensated by some of the partners shown, which may affect which offers appear and where. It does not affect our reporting or recommendations. See our editorial standards.