[Z-man]

For reference: one extra payment a year on a 30 year loan drops down the term of the mortgage to 22 years.

If you are able to double-up on the payments now, then assuming you have a 30-year loan, why not just refinance to a 15 year mortgage? They way, you make one (larger) payment a month, have a lower interest rate, and can pay off your mortgage sooner.

If you are borrowing 200k, there here's a comparison between a 15 year loan at 3.5% vs. a 30 year loan at 4.5%:

15 Year
Loan amount $200,000.00
Interest rate 3.500
Term of loan - years 15

Monthly interest rate 0.003
Term of lean - months 180
Est. montly mortgage $1,429.77

Total amount $257,357.71
Total interest $57,357.71

30 year loan
Loan amount $200,000.00
Interest rate 4.500
Term of loan - years 30

Monthly interest rate 0.004
Term of lean - months 360
Est. montly mortgage $1,013.37

Total amount $364,813.42
Total interest $164,813.42

There is a huge difference in the total cost of the loan when comparing a 30 year vs. a 15 year. you can easily create a mortgage calculator in Excel that can show you the numbers. (Or PM me and I can send you my spreadsheet).

If you can already afford a 15 year mortgage, why not just refinance to a more attractive rate?

-Z