Compare the two fixed-rate paths
Closing cost difference is 15-year costs minus 30-year costs. Use a positive number if the 15-year quote costs more upfront and a negative number if it costs less.
| Path | Rate | Monthly P&I | Upfront difference | Interest at horizon | Balance at horizon | Total horizon cost | Total interest | Payoff time |
|---|
Total horizon cost is interest paid through the holding period plus upfront cost difference. Principal repayment is shown separately as equity because it reduces debt.
Methodology notes
Payment and interest
Payments use the fixed-rate amortization formula. Each monthly step calculates interest from the remaining balance, then applies scheduled and optional extra principal.
Holding-period cost
Horizon cost includes interest and the entered closing cost difference. It does not include taxes, insurance, PMI, deductions, opportunity cost of down payment, or future refinance terms.
Investment scenario
The optional return applies only to the monthly payment difference that a 30-year borrower could invest. It is a sensitivity test, not a guaranteed or risk-adjusted result.
Results are estimates for educational purposes only and are not financial advice. Affordability, cash reserves, job stability, refinance risk, and behavioral follow-through can matter more than the lowest modeled cost. See full disclosure.
15-year vs 30-year FAQ
Why is the 15-year payment so much higher?
The same loan balance has to be repaid in half the time. A lower rate can help, but the shorter amortization schedule drives the payment.
Is the 30-year safer?
It can be safer for cashflow because the required payment is lower. That flexibility has value if your income varies or you need to protect emergency reserves.
Can I switch later?
You may be able to refinance later, but future rates, closing costs, qualification, income, home value, and lender standards are uncertain.