The Real Break-Even on Prepaying a Home Loan Isn't the Interest Rate

The standard advice is to compare the loan’s interest rate to what the money could earn invested instead - prepay if the loan rate wins, invest if the expected return wins. That comparison treats the loan rate as the only variable that matters, and it’s missing one: how many years are left on the loan changes constantly, and it decides how much a rupee of prepayment is actually worth.

Take a ₹50 lakh loan at 8.5% over 20 years. Every EMI is the same fixed amount, but what it’s made of changes completely over the loan’s life:

Interest as a share of that year’s EMI payments, over a 20-year, ₹50 lakh loan at 8.5%.

In year 1, 81% of every EMI is interest. By year 18, that’s down to 19% - most of the EMI is now principal. The loan’s stated rate, 8.5%, hasn’t moved at all. What’s moved is the remaining tenure the rate has left to compound against.

The Same Rupee Is Worth Four Times More in Year 1

That difference has a direct rupee value. Prepay ₹1 lakh in year 1, with 19 years left on the loan, and the guaranteed benefit - avoided interest, compounding at 8.5% for those 19 years - is worth roughly ₹4.71 lakh. Prepay the identical ₹1 lakh in year 18, with 2 years left, and the guaranteed benefit is worth roughly ₹1.18 lakh. Same rate, same rupee amount, a four-times difference in what the prepayment actually delivers - purely a function of when in the loan’s life it happens.

Remaining Tenure, Not the Rate, Sets the Bar

This is why “prepay if the loan rate beats my expected investment return” is an incomplete rule. Prepaying early locks in that guaranteed rate over a long horizon - a genuinely high bar for a risky investment to clear with any confidence. Prepaying late locks in the identical rate over a much shorter horizon, where the guaranteed amount at stake is smaller and a few years of equity returns going either way matters less to the outcome either way. The rate never changes. What a rupee of prepayment is worth does - and it’s highest exactly when most borrowers have the least spare cash to act on it.

Weigh the prepayment against remaining tenure, not against the headline rate. Early prepayment locks a guaranteed return over a long horizon and sets a high bar for any risky alternative - and it is worth most exactly when most borrowers have least spare cash.