Blend-and-Extend Mortgage or Wait for Renewal: The Actual Math

Your lender calls with an offer. Rates have come down, and instead of waiting two more years at 5.79% you can blend into a new five-year term today at something in the high fours. No penalty, no paperwork, just a better rate. It sounds like a gift.

It is not a gift. It is an average, and once you can compute the average yourself you can see exactly what the lender is charging you for it.

What a blend actually does

A blend-and-extend replaces your current rate with a weighted average of your existing rate and the lender's current rate for the new money and the new time. The weighting is by months.

Blended rate = (months remaining × your current rate + months added × the new rate) ÷ total months of the new term

There is a second version. A blend-to-term keeps the original maturity date and blends only over the months left, which is what you get when you increase the mortgage without extending. A blend-and-extend resets the clock to a full new term. They produce different numbers, so ask which one is on the table.

A worked example

Illustrative figures, not current market rates. A $500,000 balance, 24 months left on a fixed term at 5.79%, and a lender offering 4.29% on a new five-year term.

Look at what the blend produced. 4.89% is not the market rate of 4.29%, because you are still carrying two years of 5.79% inside the average. And it is not worse than waiting either: if you wait and the market is still at 4.29% in two years, your five-year cost is identical to the blend by construction. That is the whole insight. Blending is roughly neutral against waiting. The lender designed it that way.

What you actually buy with a blend is certainty. You are trading the chance that rates are lower at renewal for protection against the chance that they are higher. What you give up is the ability to take your business to another lender at renewal, which is often worth more than people assume.

The option that is not neutral: breaking

Breaking the mortgage is the only one of the three that changes the answer materially, because it puts you at the market rate for the whole period. It costs a penalty.

• Variable rate: usually three months' interest. On $500,000 at 5.79% that is roughly $7,200, and the calculation is simple enough to check yourself.
• Fixed rate: the greater of three months' interest or the interest rate differential. The IRD is where lenders differ enormously, because some calculate it against posted rates rather than the discounted rate you actually pay, which can multiply the number.

The break-even is straightforward. Compare the penalty against the interest you save on the remaining term only. In the example, saving 1.5 percentage points on $500,000 for two years is around $15,000 of interest. If the penalty is $9,000, breaking wins by roughly $6,000. If the penalty is $22,000 because of a posted-rate IRD, waiting wins comfortably.

One thing a blend has going for it: because you stay with the same lender and the loan is not being re-advanced, a blend generally does not put you through a fresh qualification. Breaking and moving to a new lender might. That interacts directly with what happens to the stress test when you switch at renewal.

How to decide in four steps

1. Get three numbers from your lender in writing: your current rate, the exact months remaining, and today's penalty to break.
2. Compute the blended rate yourself with the formula above, and ask the lender to confirm it. A gap between the two is the lender's margin, and it is negotiable.
3. Price the break: penalty versus the interest saved over the remaining months only, not over the new term.
4. Shop the market rate independently, through a broker or two other lenders, so the comparison is against the real market rather than your lender's retention desk.

Run each rate through the mortgage calculator to convert percentages into the payment you will actually make, and check the mortgage stress test guide before assuming you can move lenders at all.

When each option genuinely wins

There is a fourth situation worth naming: if you are likely to sell within the term, none of this matters as much as the transaction costs, and the cost of selling calculator will show you why.

Frequently asked questions

Is blend-and-extend worth it in Canada?

It is priced to be roughly neutral against waiting, so the value is rate certainty rather than savings. It is worth it when you expect rates to rise and you intend to stay with the same lender.

How is a blended mortgage rate calculated?

Weight your current rate by the months remaining and the new rate by the months being added, then divide by the total months of the new term. Ask your lender to confirm the figure; a difference between their number and yours is margin.

Does blending a mortgage cost a penalty?

Usually not directly. Some lenders fold a portion of the interest rate differential into the blended rate instead of charging it up front, which is a penalty by another name. Ask explicitly whether any penalty is built into the rate.

Is it cheaper to break my mortgage than to blend?

It can be. Compare the penalty against the interest saved over the remaining months only. Breaking wins when the rate gap multiplied by the remaining term exceeds the penalty, and you can still qualify elsewhere.

Do I need to requalify to blend and extend?

Generally not, because you stay with the same lender and are not being advanced new funds. Adding money to the mortgage as part of the blend can change that.

Sources

• FCAC: Renewing your mortgage
• FCAC: Prepayment penalties
• FCAC: Choosing a mortgage term