The actual saving over 20 years: what a lower home loan rate can mean
A R4.15 million South African home loan case study: nearly R956 000 less in repayments — and two very different ways to put the monthly saving to work.
A small rate difference. A big long-term impact.
Mortgage Gateway · 18 October 2026 · 6 min read
A difference of a few thousand rand a month can feel small beside the price of a home. Across 240 instalments, however, a lower home loan interest rate can make a substantial difference. In the client example supplied by Mortgage Gateway, a negotiated rate of 9.75% is compared with an earlier offer of 11.18% on the same R4 150 000 loan.
R3 982
Lower monthly instalment
R955 657
Less repaid over 20 years
4 years 6 months
Earlier payoff with extra payments
The application: four banks, different answers
Mortgage Gateway submitted the application to four banks. Two approved it and two declined, including the bank the client already used. The account describes a 9.75% negotiated offer and an 11.18% offer, followed by further negotiation that brought the higher-rate bank to 9.75%.
The client accepted a 9.75% offer, described as prime minus 1% at the time of the offer. The comparison below measures that rate against the earlier 11.18% quote. It does not imply that 11.18% was the only available alternative or that every applicant will receive these rates. Banks are unnamed to preserve the case study’s anonymity.
Compare home loan repayments over 20 years
Same loan amount. Same term. A 1.43 percentage-point interest rate difference.
| Loan detail | Accepted rate | Earlier higher-rate offer | Difference |
|---|---|---|---|
| Loan amount | R4 150 000 | R4 150 000 | — |
| Annual interest rate | 9.75% | 11.18% | 1.43 percentage points |
| Monthly instalment | R39 363 | R43 345 | R3 982 |
| Total repaid | R9 447 228 | R10 402 884 | R955 657 |
| Total interest | R5 297 228 | R6 252 884 | R955 657 |
At these unchanged rates, the lower offer reduces the instalment by about R3 982 a month and total repayments by R955 657. This is the loan-cost saving — not a R3 million cash saving.
Option 1: invest the monthly saving
A projected R3.02 million investment balance — not a guaranteed return.
Suppose the client invests the full monthly difference at the end of every month for 20 years, earning a constant nominal 10% annual return compounded monthly. Here is the illustration:
| Investment assumption or result | Amount |
|---|---|
| Monthly deposit | R3 982 |
| Total contributed | R955 657 |
| Projected growth | R2 068 076 |
| Projected future value | R3 023 732 |
| Value in today’s money at 6% annual inflation | R942 814 |
The projected balance includes both the contributions and their growth. It is not an additional saving on top of those contributions. At assumed inflation of 6% a year, that future balance has purchasing power equivalent to approximately R942 814 today.
A 10% investment return is an assumption, not a promise. Fees, taxes, investment risk and changing inflation can affect the result; they are not included in this illustration.
Option 2: pay off the bond earlier
Keep the higher instalment, but pay it into the lower-rate bond.
Instead of investing, the client could pay approximately R43 345 each month into the 9.75% loan — the lower instalment plus the monthly saving. The additional amount reduces the outstanding capital, so less interest accrues thereafter.
| Loan detail | 11.18% standard | 9.75% standard | 9.75% plus extra |
|---|---|---|---|
| Monthly payment | R43 345 | R39 363 | R43 345 |
| Time to repay | 20 years | 20 years | 15 years 6 months |
| Total repaid | R10 402 884 | R9 447 228 | R8 059 704 |
| Total interest | R6 252 884 | R5 297 228 | R3 909 704 |
The final payment in month 186 is approximately R40 814. The bond is cleared 54 months sooner, with about R1 387 524 less interest than the standard 9.75% schedule and R2 343 180 less repaid than the original higher-rate schedule.
These results depend on the loan rate staying at 9.75% and payments continuing as assumed. A prime-linked rate can change. Paying down debt avoids interest at the applicable loan rate, rather than generating a guaranteed investment return. Check your bank’s extra-payment conditions and keep an appropriate emergency reserve.
The bottom line: compare, negotiate, then choose
Comparing multiple bank offers gives a bond originator a basis for negotiating. This example shows why the monthly instalment is only the start: a better rate may lower lifetime borrowing costs, free up money for investing, or help you become debt-free earlier.
Thinking of buying a home or refinancing? Mortgage Gateway submits your application to multiple banks and negotiates on your behalf, at no cost to you. The rate and approval outcome depend on your circumstances and each lender’s assessment.
Calculation notes: monthly interest equals the annual rate divided by 12; payments and investment deposits occur at month-end. Full-precision instalments are used in calculations and figures are rounded independently for display, so rounded rows may differ by R1. No loan fees, insurance, investment fees or taxes are included. Rates, returns and inflation are held constant for illustration only. This is not financial advice.
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