Prepay Your Home Loan or Invest in SIP? Here's the Actual Math (2026)

You have ₹20,000 extra every month. Or a ₹3 lakh bonus just landed. The question that follows is one of the most fiercely debated in Indian personal finance: Kill the home loan faster, or invest the money? Both camps are loud. The math, however, is quiet and clear. Let's do it properly.

The Core Math: Loan Rate vs Expected Returns

The decision reduces to one comparison:

Your loan interest rate (post-tax) vs your expected investment return (post-tax).

• Home loan rate in 2026: ~8–9%
• Long-term equity SIP returns (historical): 11–13%, taxed at 12.5% LTCG → ~10.5–11.5% post-tax

On pure expected value, investing wins by ~2.5–3.5% per year. On ₹20,000/month over 15 years, that gap compounds into a difference of ₹25–35 lakh. Run your own numbers in the SIP Calculator against your loan's interest schedule. But — and this matters — the loan's 8.5% is guaranteed savings, while the SIP's 12% is a probable return. Prepayment is a risk-free bond paying your loan rate. That's why the honest answer depends on three more things.

The 3 Deciders

1. Tax benefits shrink your effective loan rate

Under the old tax regime, home loan interest gives you up to ₹2 lakh deduction (Section 24b) plus ₹1.5 lakh on principal (80C). For a 30%-slab taxpayer, an 8.5% loan effectively costs ~6–6.5%. Beating 6.5% with a long-term SIP is historically very likely → investing wins clearly. Under the new regime (no interest deduction on self-occupied homes), your loan costs the full 8.5% → the gap narrows, and prepayment becomes more competitive.

2. Where you are in the loan's life

EMIs are interest-heavy in the first 5–7 years. Prepaying ₹5 lakh in year 2 of a 20-year loan can cut 3+ years of tenure. The same prepayment in year 15 saves very little — that money should almost certainly be invested instead.

3. Your sleep-at-night factor

Debt is emotional. If EMI stress affects your decisions, career risk-taking, or family peace — prepaying has a return no spreadsheet captures. Finance is meant to serve your life, not the other way around.

The Hybrid Strategy (What We'd Actually Do)

You don't have to pick a side. The highest-satisfaction approach for most households:

1. Secure the base first — 6-month emergency fund before either option. (How big should it be?)
2. Split the surplus 50:50 — half to prepayment, half to equity SIP. You de-risk *and* compound.
3. Prepay with bonuses, invest the monthly surplus. Lump sums attack the principal hardest early in the tenure; monthly flows get rupee-cost averaging. (Why monthly flows suit equity: SIP vs Lump-Sum — 30 Years of Data)
4. Step up the SIP yearly. As increments arrive, raise the SIP 10% each year — the compounding effect is dramatic. See it yourself in the Step-Up SIP Calculator.
5. Re-run the math when rates change. If loan rates spike above 10% or you move tax regimes, the balance shifts.

Decision Cheat-Sheet

The Bigger Question: What's the Money For?

"Prepay vs invest" is really a question about your goals. If you're building towards financial independence, being debt-free at retirement *and* having a full corpus are both requirements — the question is sequencing. Two reads that go deeper: How Much Money Do You Need to Retire Early in India? and Why a Single Projected Number Lies to You — Monte Carlo Planning. Or skip the spreadsheets: Aurelian Capital's free goal planner models your loan, your SIPs, and your goals together — and shows the probability of each path working across 10,000 market scenarios.