Mortgage Refinance Break-Even Calculator

WHAT IT DOES

This userscript helps homeowners decide whether refinancing makes financial sense by calculating the break-even point. It scans mortgage refinance pages, loan calculators, or bank websites for current loan details—remaining balance, interest rate, monthly payment, loan term, and closing costs. It displays an interactive calculator panel to calculate the break-even point for refinancing, extract figures from text, calculate monthly savings from a lower rate, determine the number of months to recoup closing costs, and show the total savings over the life of the loan. The script compares multiple refinance scenarios, shows the break-even timeline, highlights the best offer, and exports the analysis as CSV or HTML. It suggests whether refinancing makes financial sense based on how long you plan to stay in the home.

WHERE IT RUNS

The script works on mortgage refinance pages, loan calculators, bank websites, and any page with loan data. It runs entirely within your browser, reading only the visible content of the current page. It does not track your browsing history, access other tabs, or send any data externally. All loan data is processed and stored locally.

HOW TO USE

After installation, open the panel by clicking the tool's icon in the BotGentz sidebar. Enter your remaining balance, current interest rate, current term, current monthly payment, new interest rate, new term, closing costs, and how long you plan to stay. Click "Calculate Break-Even" to see monthly savings, break-even point, total savings, and a recommendation. A savings timeline bar chart shows when you break even. Use "Extract from page" to auto-fill loan details from the current page. Use the export dropdown to choose your format—CSV or HTML (report). Click "Export" to download.

THE TECHNICAL MECHANISM

This script uses standard mortgage amortization formulas to calculate the break-even point. The monthly payment is calculated using the formula: P = principal × (r(1+r)^n) / ((1+r)^n - 1), where r is the monthly interest rate and n is the number of months. The current payment is either user-provided or calculated from current rate and term. Monthly savings = current payment - new payment. The break-even point is calculated as closing costs divided by monthly savings (in months). Total savings over the remaining term is calculated as (monthly savings × remaining months) - closing costs. The recommendation compares the break-even period to the planned years of staying in the home. The savings timeline tracks cumulative savings year by year and is displayed as a bar chart. All data is persisted using GM_setValue.

THE PANEL

The panel is draggable anywhere on the screen and remembers its position between sessions. It can be collapsed to a small floating bubble to minimize distraction, and expanded again with a single click. The panel's width can be adjusted, and pressing the Escape key closes it instantly. All settings and loan data are persisted locally using GM_setValue, so your calculations remain intact across page reloads and browser restarts.

PLEASE NOTE

This userscript requires the free BotGentz extension to function. The script extracts figures from page text—it may not capture all numbers correctly. Review and adjust extracted data as needed. The calculations are estimates based on the data provided and do not account for all loan fees or tax implications. The script does not access external APIs or store any data outside your browser. No data from your browsing is stored or transmitted anywhere—all processing occurs entirely in your browser.