In this scenario we take the payment in Scenario 2 - $632.41/month base payment and an additional principal payment of $300.00/month and switch to accelerated bi-weekly payments of $316.20 with an additional principal payment of $150.00 {this results in one additional payment of $632.41 + $300.00 per year} The result is the effective amortization is reduced to 15.5 years and the total interest paid is reduced by $40,108.04 (51.6%)