Fixed-Then-Variable (Hybrid) Rate Comparison

Understanding the hybrid (fixed-then-variable) mortgage comparison — concept and principle

A hybrid mortgage charges a lower fixed rate for the first few years, then switches to a variable rate for the rest of the term. This calculator compares that loan with a loan fixed for its whole life, using the variable rate you expect after the switch, and tells you which costs less in total interest. Change the expected variable rate to stress-test the hybrid option.

How it is calculated

Both loans use the standard amortizing payment A = P × i ÷ (1 − (1 + i)^−n), with monthly rate i = annual rate ÷ 12 and n months.

• Hybrid, first period: payment at the fixed hybrid rate over the full term.
• Balance at the switch: what remains after K payments, B = P(1 + i)^K − A × ((1 + i)^K − 1) ÷ i.
• Hybrid, after the switch: B is re-amortized at the variable rate over the remaining N − K months.
• Hybrid interest = A1 × K + A2 × (N − K) − P; fixed interest = A × N − P.

The principle

During the fixed period the hybrid charges less, but the balance falls slowly because a 30-year loan pays mostly interest in its early years. When the rate resets, that still-large balance is spread over fewer months at the new rate. Whether the hybrid wins depends on how its early saving compares with the cost of the later rate. For the default loan, the break-even variable rate is about 6.29%.

Worked example

1. Inputs: 300,000 over 30 years; full fixed 6%; hybrid 5.2% for 5 years, then 6.5%.
2. Hybrid payment = $1,647.33 for 60 months; balance after 5 years about 276,258.33.
3. Re-amortized over 300 months at 6.5%: $1,865.32.
4. Hybrid interest = 1,647.33 × 60 + 1,865.32 × 300 − 300,000 = $358,434.78.
5. Fixed payment = $1,798.65; interest = 1,798.65 × 360 − 300,000 = $347,514.57.
6. Full fixed is cheaper by 358,434.78 − 347,514.57 = $10,920.21.

How to read the result

The hybrid saves about 9,079 in payments during the first five years, but loses more later at 6.5%. If you will probably sell or refinance before the reset, the early saving matters most. If you will keep the loan, test a few plausible variable rates and check that you can afford the higher payment.

Common mistakes

• Comparing only the first payment instead of total cost over the expected holding period.
• Assuming the variable rate stays fixed after the reset; it can change every adjustment period.
• Ignoring refinancing fees, early repayment charges and rate caps written into the contract.

Frequently asked questions

Which is safer, hybrid or fully fixed?

Fully fixed: the payment never changes, so a rise in rates cannot hurt you.

When is a hybrid loan better?

When you expect to sell or refinance before the fixed period ends, or expect rates to be lower after the reset.

Does the calculator model several rate changes?

No. It applies one variable rate to the whole period after the switch, as a scenario.

Sources: Consumer Financial Protection Bureau (CFPB), Consumer Handbook on Adjustable-Rate Mortgages.