Calculation sequence
- Model the current loan from balance, rate, remaining term and repayment frequency.
- Model the new rate over the same remaining term using the same principal. This isolates the rate effect.
- Model the proposed refinance using the lender's proposed term and any financed switching fees.
- At each repayment period, compare current-loan interest with refinance interest plus net switching cost.
- Call break-even only when the advantage becomes non-negative and does not turn negative again through the full modeled horizon.
- If you enter a holding period, show the modeled saving or additional cost at that checkpoint separately from lifetime economics.