How to Run the Numbers on a Home Loan Refinance: A Worked Example

The Decision That Sits on a Lot of Kitchen Tables

Imagine a family who bought a house in Pune for ₹68 lakhs. They put down ₹13 lakhs and financed the remaining ₹55 lakhs through a nationalized bank at 8.75% for a 20-year term. At the time, it felt like the best they could get — rates were climbing, the property was slipping away, and the EMI of ₹48,560 fit, just barely, within their monthly budget.

Two years later, a private-sector bank offers them 8.05% on a balance transfer. A relative did the same and "saved a lot." But what does that actually mean? That's the question worth answering — not with gut feel, but with actual numbers laid out side by side. The figures below are a worked illustration, but the method applies to any real refinance decision.

Where You Stand After Two Years

Before evaluating any new offer, you have to know exactly where you are. After 24 EMI payments at ₹48,560 on a ₹55 lakh loan at 8.75%, the amortization schedule would look roughly like this:

Original principal: ₹55,00,000
Total paid over 24 months: ₹11,65,440
Interest paid in those 24 months: ₹9,14,320
Principal repaid so far: ₹2,51,120
Outstanding balance: ₹52,48,880

This is the part that surprises most people. After two full years of diligently paying nearly ₹50,000 a month, the principal has barely moved. This is how front-loaded amortization works — your early EMIs are almost entirely interest. Many borrowers assume they've paid off ₹6-7 lakhs of principal by this point; the real figure is far smaller, and seeing it can be a shock.

The New Offer on the Table

Suppose the competing bank's offer reads as follows:

New interest rate: 8.05% (floating, RLLR-linked)
Loan amount: ₹52,48,880 (outstanding balance transfer)
Remaining tenure: 18 years (216 months)
Processing fee: 0.5% of loan amount = ₹26,244
Legal/valuation charges: ₹8,500
Foreclosure fee (existing bank): Nil (RBI mandates zero foreclosure charges on floating-rate loans)

Total one-time cost to switch: ₹34,744

The new EMI at 8.05% on ₹52,48,880 over 216 months comes to about ₹44,190 — a monthly saving of roughly ₹4,370.

Building the Before-and-After Schedule

A single EMI comparison tells you nothing useful on its own. What matters is the total interest outflow over the life of the loan. Here's how the two scenarios would stack up from the decision point onward:

Scenario A — Stay with the existing bank (8.75%, 216 months remaining):

Monthly EMI: ₹48,560
Total payments over 18 years: ₹1,04,89,760
Total interest to be paid: ₹52,40,880

Scenario B — Refinance at 8.05% (216 months):

Monthly EMI: ₹44,190
Total payments over 18 years: ₹95,45,040
Total interest to be paid: ₹43,00,160 (approximate, accounting for the transferred balance)
Plus one-time switching cost: ₹34,744
Total effective outflow: ₹95,79,784

The interest saving by switching: roughly ₹9,10,000 over 18 years. After subtracting the ₹34,744 in switching costs, the net benefit lands near ₹8,75,000.

The Break-Even Calculation

Saving ₹8.75 lakhs sounds impressive, but that number only fully materializes if the borrower stays in the loan for the entire 18 years. The more immediate and practical question is: when does the switch start paying for itself?

The break-even formula is simple:

Break-even (months) = Total switching cost ÷ Monthly saving

₹34,744 ÷ ₹4,370 = about 7.95 months — roughly 8 months.

In other words, if the family plans to stay in this home for at least eight more months, refinancing is mathematically justified. For anyone with no plans to sell for 5-7 years, that's a clear win.

What the Schedule Looks Like Month by Month

To make this concrete, here's a snapshot comparing the two schedules for the first 12 months after the decision point:

Month 1: Old EMI ₹48,560 — interest ₹38,232, principal ₹10,328. New EMI ₹44,190 — interest ₹35,228, principal ₹8,962. Net monthly saving: ₹4,370.
Month 6: Old schedule interest component ₹38,084; new schedule ₹35,021. Cumulative saving so far: ₹26,220 — about 75% of the switching cost recovered.
Month 8: Cumulative saving crosses ₹34,960. Switching cost fully recovered. Every rupee from here is net gain.
Month 12: Cumulative saving: ₹52,440. Net gain after switching cost: ₹17,696.

By year three, a family in this position would be ahead by over ₹1.5 lakhs in cash terms — money that either stays in their account or gets reinvested.

The Risks That Are Easy to Ignore

Two things can quietly undermine an analysis like this, and they're worth highlighting because they apply to almost every refinance decision.

The floating-rate gamble: A new 8.05% rate tied to the bank's Repo-Linked Lending Rate (RLLR) moves up if the RBI raises rates. The existing loan may also be floating, but the spread above RLLR can differ. In a falling-rate environment, the new bank tends to benefit the borrower more; in a rising one, the advantage narrows. There's a judgment call here on rate trajectory — not a certainty, just a directional view.

The tenure trap: A bank representative might suggest resetting the tenure to 20 years instead of 18. That would drop the EMI further — to around ₹40,900 in this example — but the total interest outflow would increase by nearly ₹4 lakhs compared with simply staying put. This is one of the most common refinance mistakes: lowering the EMI by stretching the tenure and calling it a win. It isn't.

Keeping the tenure at the remaining 18 years should be non-negotiable.

Following the Decision Through

A refinance like this typically takes about three weeks — document collection, legal verification of the title, and the new bank's processing — after which the old loan is closed and the new one begins.

Roughly eight months in, the switching cost is fully recovered. From there, an early prepayment compounds the benefit. A one-time prepayment of ₹1,50,000 — say, from an annual bonus — made in month 9 of the new loan could eliminate roughly 11 future EMIs and save around ₹38,000 in interest, because prepayments made early in a loan's life have an outsized impact on interest savings.

Three Takeaways for Anyone Considering a Refinance

A case like this isn't unusual — it's fairly typical of what a well-executed home loan refinance can look like. A few principles it illustrates clearly:

The rate gap matters more early in the loan. Waiting another 8 years to refinance would leave a much smaller remaining principal, shrinking the benefit. Refinancing tends to make the most sense in the first half of a long-tenure loan.
Never extend the tenure to chase a lower EMI. If the bank suggests resetting to the original term, reject it. Match the remaining tenure or go shorter — never longer.
Calculate break-even before anything else. The total switching cost divided by the monthly saving gives you a number in months. If that number is less than your expected remaining ownership period, the math likely works in your favor.

What a careful borrower ultimately gains isn't just money — it's clarity. Months of a folder of papers sitting on the kitchen table are months of uncertainty. Running the actual numbers takes less than an hour. That's the value of doing the math before making the call.