The Lowest Rate Isn't the Cheapest Mortgage

On a $500,000 home, putting down $50 less can add more than $11,000 to your mortgage.

That is the difference between a 20% down payment and 19.99%. Cross that line and mortgage default insurance usually enters the bill. A lower interest rate might come with it. Whether you come out ahead takes a little more arithmetic.

Rooofread ran the comparison. In one example, the buyer with the lower rate pays about $6 more each month and ends five years roughly $9,562 worse off on borrowing costs.

The rate is smaller. The loan is bigger. Both numbers matter.

Why an Insured Mortgage Can Get a Lower Rate

With less than 20% down, a typical eligible home purchase requires mortgage default insurance through CMHC, Sagen or Canada Guaranty. You pay for it. It protects the lender if you cannot repay the mortgage.

That protection reduces the lender's risk and can help it offer a lower interest rate. It does not make your own payments optional, and it is different from insurance that pays your mortgage after death or illness.

There is no universal rule that the smallest down payment gets the best deal. Pricing depends on the lender, property, borrower and mortgage conditions. Compare quotes you actually qualify for.

The rates below are illustrative assumptions, not advertised offers or a claim about October's best rates. They let us test the idea without pretending everyone's quote will be the same.

The $50 Decision With an $11,201 Premium

Take a $500,000 home and a 25-year amortization, the planned time to repay the loan.

At 20% down, you contribute $100,000 and borrow $400,000. Our example assumes no borrower-paid default insurance on that mortgage.

At 19.99% down, you contribute $99,950 and borrow $400,050 before insurance. CMHC's standard premium in that bracket is 2.80% of the mortgage amount. That is $11,201.40, not 2.80% of the home price.

Add the premium to the mortgage and the opening balance becomes $411,251.40. You can instead pay the premium upfront, but that does not make it disappear. Financing it means paying interest on it while it remains in the loan.

In Ontario, 8% provincial tax adds another $896.11, payable at closing rather than added to the insured mortgage. We include that tax in the example. Buyers elsewhere should use their province's treatment.

Notice the cash consequence: putting down $50 less has created an $896 closing bill. This version does not even leave you with more cash on closing day.

What Five Years Actually Costs

Assume a five-year fixed rate of 4.54% with 20% down, compared with 4.29% at 19.99% down. Both mortgages use monthly payments and a 25-year amortization.

The lower rate saves about $2,536 in interest. The premium and its tax cost about $12,098. The difference is $9,562 more for the insured option.

That last row measures borrowing costs. Paying down the original house loan builds equity, so we do not treat it as a fee that vanishes. This is also why simply comparing monthly payments misses part of the story: you need to know how much debt remains.

For another way to check the comparison, add the down payment, all 60 payments, remaining balance and upfront premium tax, then subtract the common $500,000 purchase price. It gives the same result. Do not add a financed premium again: it is already inside the payments and balance.

Would a bigger rate discount change the answer? Yes, eventually. At 4.79% uninsured versus 4.24% insured, the insured option still costs about $3,784 more over five years. Against the original 4.54% uninsured quote, the insured rate needs to fall to about 3.80% to break even under these assumptions. That is a gap of roughly 0.74 percentage points.

This is a threshold for this example, not a rule for every mortgage. The premium, tax, term and actual quotes can all move it.

What If You Want to Keep $50,000 in the Bank?

Now compare 10% down with 20% down on the same home, using 4.29% insured and 4.54% uninsured again.

With 10% down, the $450,000 base mortgage carries a 3.10% premium: $13,950. Finance it and you start owing $463,950. The Ontario premium tax is $1,116, and the monthly payment is about $2,514.

Over five years, interest, premium and tax total about $107,856, compared with $84,785 at 20% down. That is approximately $23,070 extra before allowing for any earnings on money you keep.

You have held back $50,000 of the down payment, or $48,884 after the extra Ontario tax. The calculation already accounts for putting less money into the house. You cannot subtract that $50,000 from the $23,070 again. What could reduce the gap is the return that retained money earns, after tax and fees, along with any differences in how you save the monthly payment gap.

An emergency fund has a different kind of value. If putting 20% down leaves you borrowing on a credit card when the furnace fails, the cheapest mortgage calculation has missed something about your life.

Keeping cash can be sensible. It still has a cost. Price the trade-off before deciding how much cash you can comfortably turn into home equity.

How Much Down Payment Do You Need for a House in Canada?

For a typical eligible owner-occupied home with one or two units, the minimum is 5% on the first $500,000 and 10% on the portion above that, while the price remains below $1.5 million. At $1.5 million or more, the minimum is 20%. Approval can require more.

That means $25,000 on a $500,000 home, $55,000 on an $800,000 home and $95,000 on a $1.2 million home. At exactly $1.5 million, it becomes $300,000. These are down payments, not the whole amount you need to close.

If you do not have 20%, the relevant comparison may be buying with insurance versus continuing to rent and save. On the $500,000 example, 5% down means a $475,000 base mortgage and a standard 4% premium of $19,000, before any applicable tax or surcharge.

That premium buys access to a mortgage with less money upfront. Whether buying sooner makes sense also depends on rent, saving capacity, ownership expenses, moving plans and what happens to prices. This comparison does not assume buying now wins.

Use The Real Number to look beyond the mortgage payment. If a job move is part of the decision, You got the job. So where's the house? looks at the housing costs a salary offer can leave out.

The Details That Can Change Your Quote

Ask about an insurable mortgage. Some mortgages with 20% or more down qualify for insurance the lender buys at its own expense. That can affect pricing. Eligibility is narrower than “20% down”: CMHC's standard low-ratio purchase criteria include a price below $1 million and a maximum 25-year amortization. Ask which pricing category your actual loan fits.

Separate the term from the amortization. A five-year fixed term locks the rate for five years. It does not promise that rate for 25 years. Insured 30-year amortizations are available to eligible first-time buyers or buyers of newly built homes; CMHC adds 0.20 percentage points to the premium rate for amortizations over 25 years. That is an insurance charge, not an extra 0.20 points on the mortgage interest rate.

Keep your insurance certificate. Existing coverage can help when you switch lenders at renewal. Give the new lender the certificate number. Increasing the loan or extending the amortization can change the insurance requirements. Coverage does not guarantee a particular future rate. Ordinary cash-out refinancing is a different product. A specific CMHC program does allow insured refinancing to build qualifying secondary suites.

Qualification still matters. For a new purchase at a federally regulated lender, the usual stress test checks whether you can qualify at the higher of 5.25% or your contract rate plus two percentage points. A lower quoted rate does not automatically mean approval for a larger insured balance. Eligible straight switches at renewal have exceptions to the prescribed stress test.

The Question to Take to Your Broker

Ask for the same home, the same amortization and the same payment schedule priced with both down payments. Then ask for five numbers: cash due at closing, monthly payment, insurance premium, interest over the term and balance at renewal.

Compare fees, cashback conditions, prepayment privileges and the cost of breaking the mortgage too. A rate discount can lose its appeal if you need to move before the term ends.

The useful question is: “After five years, how much have I paid to borrow, how much do I still owe, and how much cash have I kept available?”

Take that answer home with the rate quote.

For the full budget around this mortgage decision, add closing costs, monthly ownership bills and the equity left at renewal.

Sources

• CMHC: mortgage insurance premium table
• FCAC: down payments, insurance and provincial tax
• Finance Canada: December 2024 mortgage reforms
• Ontario: insurance and benefits plans, retail sales tax
• CMHC: Home Start eligibility and premiums
• CMHC: mortgage insurance quick reference
• FCAC: renewing and switching lenders
• CMHC: refinancing to create secondary suites
• FCAC: preparing for a mortgage and the stress test
• OSFI: straight-switch stress-test exception