Home Loan Repayment Guide - Mortgage Planning
🏠 Understanding Home Loan Repayments
A home loan (or mortgage) is borrowed money used to purchase property. You repay this loan over time through regular payments that include both principal (the amount borrowed) and interest (the cost of borrowing).
The Home Loan Repayment Formula
Simple Example
Over 30 Years:
Shocking reality: You pay more in interest ($579k) than the original loan amount ($500k)! This shows why interest rates and loan terms matter enormously.
Components of Your Mortgage Payment
| Component | What It Is | Note |
|---|---|---|
| Principal | Amount that reduces loan balance | Increases over time |
| Interest | Cost of borrowing money | Decreases over time |
| Rates (optional) | Council rates | Some include in payment |
| Insurance (optional) | Home and contents insurance | Often paid separately |
How Payments Change Over Time (Amortization)
Example: $500k loan at 6% for 30 years ($2,998/month)
| Payment # | Principal | Interest | Balance |
|---|---|---|---|
| 1 (Month 1) | $498 | $2,500 | $499,502 |
| 60 (Year 5) | $639 | $2,359 | $467,759 |
| 180 (Year 15) | $1,058 | $1,940 | $387,204 |
| 300 (Year 25) | $1,801 | $1,197 | $237,882 |
| 360 (Final) | $2,983 | $15 | $0 |
In the first payment, only $498 goes toward principal while $2,500 goes to interest. By the final payment, nearly all $2,998 is principal. This is why paying extra early in the loan saves so much money!
Key Factors Affecting Your Repayment
1. Loan Amount (Principal)
More borrowed = higher payments. Simple and direct relationship.
2. Interest Rate
Small rate changes have huge impacts over 30 years.
| Rate | Monthly Payment | Total Interest Paid |
|---|---|---|
| 5% | $2,684 | $466,240 |
| 6% | $2,998 | $579,280 |
| 7% | $3,327 | $697,720 |
| 8% | $3,669 | $820,840 |
Just 1% difference (5% vs 6%) means paying $113,040 more in interest!
3. Loan Term
Longer term = lower monthly payment but much higher total interest.
| Term | Monthly Payment | Total Interest |
|---|---|---|
| 15 years | $4,219 | $259,420 |
| 20 years | $3,582 | $359,680 |
| 25 years | $3,221 | $466,300 |
| 30 years | $2,998 | $579,280 |
4. Deposit Size
Larger deposit = smaller loan = lower payments and less interest.
| House Price | Deposit | Loan | Monthly (6%, 30yr) |
|---|---|---|---|
| $600,000 | $60,000 (10%) | $540,000 | $3,238 |
| $600,000 | $120,000 (20%) | $480,000 | $2,878 |
| $600,000 | $180,000 (30%) | $420,000 | $2,518 |
20% deposit vs 10% deposit saves $360/month and $129,600 in interest over 30 years!
Banks typically require:
- 20% deposit minimum for most buyers
- 10% deposit possible for first home buyers (limited availability)
- Higher deposit (30-40%) for investors
Lower deposits mean higher interest rates and LMI (Lender's Mortgage Insurance) costs.
Fixed vs Floating Interest Rates
Fixed Rate:
- Interest rate locked for 6 months to 5 years
- Predictable payments
- Protected from rate increases
- Can't benefit if rates drop
- Break fees if you pay off early
Floating Rate:
- Rate changes with market (OCR decisions)
- Payments can increase or decrease
- Usually higher than fixed rates currently
- No break fees, more flexibility
- Can make extra payments anytime
Common Strategy:
Split your loan: 70% fixed (stability) + 30% floating (flexibility for extra payments).
🔢 Calculating and Comparing Repayments
Step-by-Step Calculation Example
Scenario: First Home Buyer in Auckland
Purchase Details:
Monthly Payment Calculation:
Total Cost Over 30 Years:
Comparing Loan Term Options
Same loan: $600,000 at 6.5%
| Term | Monthly Payment | Total Paid | Total Interest | Interest Saved vs 30yr |
|---|---|---|---|---|
| 15 years | $5,225 | $940,500 | $340,500 | $424,620 |
| 20 years | $4,476 | $1,074,240 | $474,240 | $290,880 |
| 25 years | $4,056 | $1,216,800 | $616,800 | $148,320 |
| 30 years | $3,792 | $1,365,120 | $765,120 | - |
Impact of Interest Rate Changes
$500,000 loan for 30 years at different rates:
| Rate | Monthly | Difference vs 6% | Annual Difference |
|---|---|---|---|
| 5.0% | $2,684 | -$314/month | -$3,768/year |
| 5.5% | $2,839 | -$159/month | -$1,908/year |
| 6.0% | $2,998 | baseline | baseline |
| 6.5% | $3,160 | +$162/month | +$1,944/year |
| 7.0% | $3,327 | +$329/month | +$3,948/year |
| 7.5% | $3,496 | +$498/month | +$5,976/year |
A 1.5% rate rise (6% to 7.5%) costs an extra $498/month or $5,976/year. This is why fixed rates provide security.
The Power of Extra Payments
Base scenario: $500k at 6% for 30 years = $2,998/month
Option 1: Pay Extra $200/Month
Option 2: Pay Extra $500/Month
Just $200/month extra saves $119k and 5 years. $500/month saves $258k and 10 years! Every extra dollar goes straight to principal, not interest. This is why paying extra early matters so much.
Weekly vs Fortnightly vs Monthly Payments
Same loan: $500k at 6% for 30 years
| Frequency | Payment Amount | Annual Total | Years to Payoff | Interest Saved |
|---|---|---|---|---|
| Monthly | $2,998 | $35,976 | 30 years | $0 (baseline) |
| Fortnightly | $1,499 (half monthly) | $38,974 | 25.5 years | $61,234 |
| Weekly | $749.50 (quarter monthly) | $38,974 | 25.5 years | $61,234 |
Affordability Guidelines
The 30% Rule:
Your mortgage payment should not exceed 30% of gross household income.
Bank Serviceability Test:
Banks test affordability at higher rates (typically current rate + 2.5-3%). They want to ensure you can still afford payments if rates rise.
Just because a bank approves $600k doesn't mean you should borrow that much. Leave buffer for:
- Rate increases
- Unexpected expenses
- Life changes (kids, job loss)
- Opportunity to save and invest
Aim for 25% of income, not 30%.
🌍 Real-World Home Loan Scenarios
Meet Sarah and Tom, both 28, buying their first home
Their Financial Situation:
House They Want:
Monthly Costs:
| Expense | Amount |
|---|---|
| Mortgage payment | $3,421 |
| Rates | $280 |
| Insurance | $120 |
| Maintenance (budget) | $200 |
| Total housing cost | $4,021 |
Affordability Check:
Their Decision:
They realized 37% was too tight. Options considered:
- Option A: Delay purchase 6 months, save another $30,000 deposit (reduces loan to $500k, payment to $3,227)
- Option B: Buy at $600,000 instead ($480k loan, $3,098/month = 28.6%)
- Option C: Buy the $650k house but plan for Sarah's upcoming $15k raise (reduces to 33%)
They chose Option B: smaller house now, upgrade later with more equity.
Mike's situation: 5 years into a 30-year mortgage
Original Loan (5 years ago):
After 5 Years of Payments:
Refinancing Opportunity:
Option 1: Keep 25-Year Term
Option 2: Keep Same $2,797 Payment
The Chen family: selling starter home, buying larger property
Current Home:
New Home Purchase:
Repayment Comparison:
| Scenario | Payment | Note |
|---|---|---|
| Old home (was paying) | $2,547 | 7% rate, 23 years left |
| New home (30-year term) | $3,341 | 6.4% rate |
| New home (20-year term) | $3,908 | Same 6.4% rate |
Their Strategy:
They chose the 20-year term ($3,908/month) because:
- Only $1,361 more than they were paying
- They're now 35-40 years old, want mortgage paid by 60
- Large deposit (38%) meant loan was manageable
- Saves $124,728 in interest vs 30-year term
Lisa's scenario: Fixed rate ending, facing higher rates
Original Loan (2 years ago):
Fixed Rate Expiring:
New Payment Shock:
How She Managed:
- Cut discretionary spending by $400/month
- Picked up 5 hours/week overtime ($280/month extra income)
- Reduced KiwiSaver from 6% to 3% temporarily ($150/month freed up)
- Total adjustments: $830/month (covered the $722 increase)
Lisa's experience is common. When rates rose in 2022-2024, many NZ homeowners faced 20-40% payment increases when refixing. Always stress-test your budget at rates 2-3% higher than current. If you can't afford that, you're borrowing too much.
🎯 Test Your Knowledge
Complete this 10-question quiz on Home Loan Repayments
Related guides
- Mortgage Repayment Strategies to Save Interest, a related guide in the same area.