re: When does it make sense, mathematically, to accelerate mortgage payments?

I don’t know your loan amount or potential extra payment amount so I can’t do the math, but go online and find an amortization calculator that lets you enter in extra payments and see how much you’ll save.

The difference between paying more towards a 6.5% loan vs putting it into a savings account earning 4.5% is not that much annually. Assuming you take the standard deduction, you’ll have to pay taxes on your savings account interest, so it decreases it even more.

Now, over the course of 30 years, it could be a 5 figure difference in total.