Home loan payment: I asked ChatGPT why the principal of my ₹90 lakh home loan hasn’t reduced despite paying off ₹45 lakh over 60 EMIs. Here is what AI said.
My ChatGPT prompt
I took a of ₹90 lakh for 25 years at 9% interest. My monthly EMI is ₹75,528. I have been paying my EMIs for 5 years, i.e., I have paid 60 EMIs, totalling ₹45 lakh (45,31,680). However, I found that my outstanding principal is ₹83,94,520. Despite paying about ₹45 lakh in EMIs, why has the outstanding principal reduced by only about ₹6 lakh?
I then asked ChatGPT to explain it to me as if I were a first-time borrower.
What ChatGPT said
A home loan = a financial product, not just ‘EMI’
When you take a loan, you’re effectively borrowing ₹90 lakh, agreeing to pay interest (cost of borrowing), and paying it back through EMIs over time.
Think of it like this:
> You’re not “buying a house with EMI”.
> You’re “renting money from the bank” and slowly buying the house.
How does EMI actually work?
Your EMI is calculated using a standard formula:
P x R x (1+R)^N / [(1+R)^N-1]
Where:
P = Loan amount ( ₹90,00,000)
R = Monthly interest rate (9% ÷ 12 = 0.75%)
N = Total months (300)
Crucial insight
The EMI is fixed, but inside it:
Interest is calculated on the remaining loan
Principal is whatever is left from EMI
So: Interest is always paid first, principal comes later.
Why does your principal barely reduce?
Month 1:
Interest = ~ ₹67,500
EMI = ₹75,528
Principal repaid = ~ ₹8,000
90% of EMI = interest
After 5 years (60 EMIs):
Total paid = ₹45.3 lakh
Principal reduced = ~ ₹6 lakh
Interest paid = ~ ₹39 lakh
Why does this happen?
This is because interest is calculated on ₹90 lakh initially, and that’s a huge base. So, early EMIs mostly serve interest.
This is called amortisation, front-loaded interest.
The hidden truth: Total cost of your loan
Let’s zoom out like an investor:
EMI: ₹75,528
Tenure: 300 months
Total paid over 25 years ≈ ₹2.26 crore
Breakdown:
Principal: ₹90 lakh
Interest: ~ ₹1.36 crore
Investor mindset takeaway
The bank earns more from your than you borrowed.
Why long tenure is a trap
Long tenure:
✔ Lower EMI (feels comfortable)
❌ Much higher total interest
Short tenure:
❌ Higher EMI
✔ Massive interest savings
Loan vs Investment: The real comparison
Your loan costs 9%. Any investment you make must beat 9% (post-tax) to make sense.
If not, prepaying the loan = guaranteed 9% return (risk-free)
What you should do now (practical strategy)
- Start prepaying early: Even ₹1–2 lakh extra per year directly reduces principal and cuts interest drastically
- Increase EMI yearly: Even a 5–10% increase can cut 5–8 years off your loan.
- Choose tenure reduction (not EMI reduction): When prepaying, always reduce tenure, not EMI.
- Treat a loan like a “negative investment”: Ask yourself whether I would invest at 9% guaranteed return? → Yes, that’s what prepayment gives you.
What most first-time borrowers misunderstand
❌ “I paid ₹45 lakh, so the loan should be reduced a lot”
✔ Reality: You paid mostly **interest**, not principal
❌ “EMI means equal payment toward the loan”
✔ Reality: Only total EMI is equal, not principal
❌ “Long tenure is safer”
✔ Reality: It’s **more expensive**
Simple analogy
Imagine you owe ₹90 lakh. Bank says: “First, pay my interest, then reduce your loan”. That’s exactly what’s happening.
SIP vs home loan prepayment? What’s better
Compare loan interest rate vs expected investment return (post-tax)
- If SIP return consistently beats 9% after tax → SIP wins
- If not → prepayment wins
Choose prepayment if:
- You want guaranteed savings
- You’re risk-averse
- You’re early in loan tenure (like you are now)
- You don’t invest regularly already
Choose SIP if:
- You can stay invested for 10–15 years
- You’re okay with market ups and downs
- You believe returns > loan cost
- You already have an emergency fund + insurance
Ideal hybrid approach:
- 60–70% → (wealth creation)
- 30–40% → Prepayment (risk reduction)
OR
- Do SIP normally
- Use bonuses/windfalls for prepayment
Your specific situation
You’re at year 5 of a 25-year loan, still in the high-interest phase. This means that prepayment right now gives maximum impact because every ₹1 prepaid saves interest for the next 20 years.
Simple rule of thumb
- If your loan rate > 8.5% → lean towards prepayment
- If your horizon > 10 years → SIP becomes attractive
If unsure, split the money.