Why early EMIs are mostly interest
Every EMI is split between interest and principal. Early in a loan, your outstanding balance is large, so most of each EMI goes to interest and very little reduces the principal. As the balance shrinks over the years, the split flips toward principal.
This front-loading of interest is why a prepayment made in year one or two saves dramatically more than the same amount paid near the end. You are removing principal that would otherwise accrue interest for the entire remaining term.
Reduce tenure vs reduce EMI
When you prepay, most lenders let you either keep the EMI the same and shorten the tenure, or keep the tenure and lower the EMI. These choices have very different outcomes.
Reducing the tenure saves the most interest, because you close the loan sooner and cut off years of interest. Reducing the EMI lowers your monthly burden and improves cash flow, but you stay in debt for the full term and save less interest overall. Choose tenure reduction if you can keep affording the current EMI; choose EMI reduction if monthly breathing room matters more right now.
Prepay or invest?
Prepaying a loan gives you a guaranteed, risk-free return equal to your loan's interest rate. Investing might earn more, but with risk and no guarantee. The comparison is between your loan rate and the return you could reliably earn elsewhere after tax.
If your loan rate is high relative to safe returns, prepaying is usually the stronger, lower-stress choice. If your loan is cheap and you are confident in higher post-tax investment returns over the same horizon, investing may win. Also weigh the intangible value of being debt-free and the liquidity you give up by locking money into a prepayment.
Watch for charges and keep liquidity
Floating-rate personal borrowing in many markets carries no prepayment penalty, but fixed-rate loans sometimes do — check before you pay. A penalty can erode the benefit of a small prepayment.
Finally, never drain your emergency fund to prepay. The interest saved is not worth taking on the risk of having no cash buffer if something goes wrong. Prepay with surplus, not with money you might need.