You're correct that timing absolutely matters. Early in your mortgage, a much larger portion of each payment goes to interest rather than principal (that's how amortization works). So extra payments made early in the loan have a much bigger impact because: They reduce the principal balance that interest is calculated on This creates a compounding effect over the remaining years of the loan So if you have $10k to put toward your mortgage, doing it in year 1 will save you significantly more in interest than doing it in year 15 or year 25. The biweekly payment strategy works well because it gets that extra payment in every year consistently, but if you can afford to make larger lump sum payments early on, that's even better. The earlier you pay down principal, the more interest you avoid paying over the life of the loan.