Two Ways to Blend Your Mortgage
When you want a lower rate but do not want to pay a prepayment penalty, most lenders offer two blending options:
| Option | What Happens | When It Applies |
|---|---|---|
| Blend to term | Blend current rate with new rate; keep same maturity date | Staying in home, modest rate improvement needed |
| Blend and extend | Blend rates; extend to a brand-new full term (usually 5 yrs) | Better rate improvement; lender’s preferred option |
Both options avoid the prepayment penalty entirely.
How the Blended Rate Is Calculated
The Simple Weighted Average
Most lenders describe blending as follows:
Blended Rate = (Outstanding Balance × Current Rate + Outstanding Balance × New Market Rate) ÷ (2 × Outstanding Balance)
Since the balance is the same on both sides, this often simplifies to:
Blended Rate = (Current Rate + New Market Rate) ÷ 2
Example:
- Current rate: 5.24%
- New 5-year market rate: 4.44%
- Blended rate: (5.24% + 4.44%) ÷ 2 = 4.84%
The Time-Weighted Calculation (Lender’s Actual Method)
Some lenders factor in remaining time differently. The more accurate calculation weights by the present value of interest payments over each period. For most borrowers, it produces a rate slightly closer to the current market rate when more than 2 years remain.
Key reality: Lenders do not always clearly disclose their blending formula. Get the offered blended rate in writing and calculate whether it makes sense given your remaining term.
Blend to Term Example
| Parameter | Value |
|---|---|
| Outstanding balance | $480,000 |
| Current rate | 5.24% |
| Remaining term | 2 years (to maturity) |
| Current 2-year market rate | 4.24% |
| Simple blended rate | 4.74% |
| Monthly payment change | $480,000 × (5.24% − 4.74%) ÷ 12 = $200/month savings |
| Total interest saved over 2 years | ~$4,800 |
| Penalty if breaking outright | ~$11,000 |
Verdict: Blend to term saves $4,800 over 2 years with no penalty vs. $11,000 penalty to break. Blend to term wins unless you need to borrow more.
Blend and Extend Example
Same borrower, but lender requires extending to a new 5-year term to get the blend:
| Parameter | Value |
|---|---|
| Outstanding balance | $480,000 |
| Current rate | 5.24% |
| Remaining term | 2 years |
| New 5-year market rate | 4.44% |
| Blended rate (extend to 5 years) | 4.84% |
| Monthly savings vs current | $480,000 × (5.24% − 4.84%) ÷ 12 = $160/month |
| Savings over 5-year new term | ~$9,600 |
| Net (vs. $0 penalty) | $9,600 saved |
But you are now locked in 3 extra years beyond your original maturity. If rates fall below 4.84% in years 3–5, you could be overpaying.
Blend and Extend vs Breaking: The Full Comparison
| Scenario | Rate | Penalty | Monthly Payment | 5-Year Total Interest |
|---|---|---|---|---|
| Keep current mortgage | 5.24% | $0 | $2,901 | $97,720 |
| Blend and extend (new 5-yr) | 4.84% | $0 | $2,740 | $89,060 |
| Break and refinance (new 5-yr) | 4.44% | $11,000 | $2,579 | $81,400 + $11,000 penalty |
| Break net (savings − penalty) | — | — | — | $81,400 + $11,000 = $92,400 |
In this scenario, blend and extend ($89,060 total) beats breaking and refinancing ($92,400 total) by about $3,340 over 5 years — without the upfront penalty.
When Blend and Extend Makes Sense
| Situation | Verdict |
|---|---|
| Rates have fallen 0.50–1.00% and you have 2+ years remaining | Usually favourable — blend avoids penalty, captures some savings |
| Rates have fallen 1.5%+ and you have 2+ years remaining | Run the math — breaking may give better 5-year savings |
| You need to borrow more (renovations, equity access) | Blend and extend typically combines with a top-up |
| Rate environment expected to continue falling | Caution — extending locks you out of future lower rates |
| You plan to sell within 2–3 years | Blend to term may be better than extending |
The Hidden Cost: Lender Discretion on Comparison Rate
Lenders set the “new rate” portion of the blend based on their current posted or advertised rates, not necessarily the best market rate. A big bank’s offered blend rate may be 0.20–0.40% higher than what a monoline would offer on a fresh mortgage.
Before accepting a blend, verify:
- What rate is being used for the “new” portion
- Whether you could get a lower rate by switching lenders (paying the penalty)
- Whether a broker could negotiate a better rate with the same lender
Blend and Extend for Top-Up Borrowing
Blend and extend is also commonly used when accessing equity. The new money is added at the current market rate, and the full balance (existing + top-up) is blended into one rate and extended.
See the mortgage portability guide for the blending math when upsizing during a move.