You can save a significant amount of mortgage interest paid if you make one additional principal and interest payment a year. This will reduce a 30-year mortgage by around 6 years. It also increases your equity in the home faster. If you choose to pay one additional mortgage payment a year by paying 1/12 of it each month (make certain to note the extra money is to reduce principal), how much will you pay each month for a mortgage of $166,000 at 3.5% for 19 years?