Today's Mortgages -- September 23: Another Day of Below 3.00% Rates for 30-Year Loans

Mortgage rates remain very low for borrowers on fixed-rate loans, but an ARM continues to be a poor option for most homeowners.

What was once unheard of has become commonplace when it comes to mortgage rates, as the average interest rate on a 30-year loan once again remained below 3.00% for Sept. 23. The average rate on a 15-year fixed-rate loan is also below 2.50% again. These rates are on par with what we've seen in recent days and weeks and remain very competitive.

Data source: The Ascent's national mortgage interest rate tracking.

30-year mortgage rates

The average 30-year mortgage rate today is 2.948%, up .002% from Tuesday's rate of 2.946%. At today's average rate, your monthly principal and interest payment will total $419 per $100,000 borrowed. Total interest costs for the life of the loan come in at $50,770 per $100,000 borrowed.

Check out The Ascent's mortgage calculator to see what your monthly payment might be and how much your loan will ultimately cost. Also learn how much money you'd save by snagging a lower interest rate, making a larger down payment, or choosing a shorter loan term.

20-year mortgage rates

The average 20-year mortgage rate today is 2.827%, down .004% from yesterday's rate of 2.831%. At today's average rate, monthly principal and interest payments would total $546 per $100,000 borrowed.

While the average rates on 20-year mortgages had been trending slightly above the average rates on 30-year loans, that's not the case today. But even with a slightly lower rate, a shorter repayment timeline means much higher monthly payments in exchange for much lower total borrowing costs. Total interest, for example, would be just $31,035 per $100,000 borrowed over the life of the loan.

15-year mortgage rates

The average 15-year mortgage rate today is 2.422%, down .002% from yesterday's average rate of 2.424%. At today's average rate, borrowers will pay $663 in principal and interest per month for each $100,000 borrowed.

Although the average 15-year rate is well below the average interest rate on a 30-year loan, higher monthly payments occur because of the shorter repayment timeline. This results in much lower borrowing costs, though, with total interest costs coming in at $19,362 per $100,000 borrowed.

5/1 ARMs

The average 5/1 ARM rate is 3.365%, up .058% from yesterday's average rate of 3.307%.

While a 30-year fixed-rate loan guarantees your rate and payment for the life of the loan, a 5/1 ARM only locks in this initial starting rate for the first five years after which time the rate and payment can change.

Taking the risk of rising rates sometimes makes sense if your initial starting rate is lower than for a fixed-rate loan and you plan to refinance or sell before rates could start rising. It does not make sense under these circumstances when the initial starting rate on the ARM is above the 30-year fixed rate. You are better off locking in your rate for the life of your loan.

Should I lock my mortgage rate now?

A mortgage rate lock guarantees you a certain interest rate for a specified period of time -- usually 30 days, but you may be able to secure your rate for up to 60 days. You'll generally pay a fee to lock in your mortgage rate, but that way you're protected in case rates climb between now and when you actually close on your mortgage.

If you plan to close on your home within the next 30 days, then it pays to lock in your mortgage rate based on today's rates -- especially since they're so competitive. But if your closing is more than 30 days away, you may want to choose a floating rate lock instead for what will usually be a higher fee, but one that could save you money in the long run. A floating rate lock lets you secure a lower rate on your mortgage if rates fall prior to your closing, and while today's rates are still quite low, we don't know if rates will go up or down over the next few months. As such, it pays to:

• LOCK if closing in 7 days
• LOCK if closing in 15 days
• LOCK if closing in 30 days
• FLOAT if closing in 45 days
• FLOAT if closing in 60 days

If you're ready to shop around, see what rates you are offered, and consider locking in your loan, it's best to get quotes from at least three different loan providers. Check out our guide to the best mortgage lenders to find the loan that's right for you.