It's one thing to say "prepaying saves interest" — it's more convincing to see the actual rupee amount. This case study walks through a realistic scenario end to end.
The scenario
A ₹30,00,000 home loan at 8.5% annual interest over a 20-year tenure, with a standard EMI of about ₹26,035. Three years in, the borrower receives a ₹1,00,000 bonus and decides to make a one-time lump-sum prepayment, opting to reduce the tenure rather than the EMI.
Why timing matters
At the 3-year mark, the outstanding balance is still close to ₹28,00,000 — most of the early EMIs went toward interest, not principal, since reducing-balance interest is charged on the full remaining balance each month. Prepaying ₹1,00,000 at this point removes that entire amount from the balance that interest gets charged on, for every remaining month of the loan.
Approximate results
| Scenario | Remaining tenure | Remaining interest (approx.) |
|---|---|---|
| No prepayment | 17 years | ≈ ₹26,80,000 |
| ₹1,00,000 prepayment at year 3 | ≈ 16.3 years | ≈ ₹25,20,000 |
A single ₹1,00,000 prepayment saves roughly ₹1,60,000 in interest and shaves about 8 months off the tenure — a return meaningfully larger than the ₹1,00,000 itself, purely from stopping future interest charges on that amount. The exact figures depend on precisely when in the schedule the prepayment lands, which is why running your own numbers matters.
The general pattern
- The earlier in the loan you prepay, the larger the interest saved — the same ₹1,00,000 prepaid in year 18 instead of year 3 would save far less, since less principal (and therefore less future interest) remains.
- Choosing to shorten the tenure (rather than lower the EMI) after a prepayment maximizes total interest saved.
- Repeating smaller prepayments regularly compounds this effect further — try our loan prepayment calculator with a recurring extra monthly amount instead of a single lump sum to see the difference.