Shopping for the best mortgage rates was supposed to have been made easier by requiring lenders to advertise more than just their interest rates, but in practice, the result doesn’t always work as well as intended. What it does do 100% of the time is to put consumers on notice that the cost of borrowing is not a simple matter.

Finding the best deal takes a little figuring.

If you’ve ever shopped mortgages, you know that you’ll see both the advertised “interest rates” and an “Annual Percentage Rate.” The APR is usually higher because it incorporates the additional loan charges and fees not shown in the nominal interest rate. The 1968 Truth in Lending Act required that the APR be included—and it would seem to be a fairer way to compare loans. If one lender requires you to pay 2% of the loan amount up-front, while another doesn’t, even if the latter has a slightly higher basic interest rate that might be more of a bargain. So going by the APR rather than just the nominal interest rate makes for a truer comparison, right?

But just as “all that glitters is not gold,” all consumer protection doesn’t necessarily work as planned. For one thing, not all APR calculations include the same costs. As points out, lenders have wiggle room. “Credit report fees, appraisal fees, and inspection fees may not be part of a given APR quote.”

Even more significant, APR calculations assume that a loan will be paid off over the full term of the loan. It spreads the other-than-interest costs equally over that term. For a standard 30-year mortgage that is paid off according to that plan, the APR is one thing. But if the median duration of homeownership in the U.S. is 13.3 years (probably an overstatement)—then a more likely APR would be significantly higher. Ditto for borrowers who refinance, because they pay off the original mortgage well short of the original term.

The upshot is that—like so many aspects of buying and selling a home—experience teaches that stepping back to take the full picture into account makes for better decision-making. When you give me the call, I’ll help you do just that!