Mortgage Payment

You currently have a 30-year fixed rate mortgage with an annual interest rate of 6%. You have had the mortgage 4 years, and on September 1, 2015 you made your 48th payment. The original principal amount was $280,000 and you monthly payment, without taxes and insurance, are $1,678.74 per month, computed using the Excel function =PMT(0.5%,360,280000,0,0).

You just received an unexpected inheritance.

You decided to apply most of it to your mortgage.

Assume that on September 1, 2015, in addition to your payment, you made a principal reduction payment of $15,000.

You will continue making your regular $1,678.74 monthly payment.

QUESTION:

How much does this large principal reduction payment shorten the life of your loan?

Compare the total interest paid over the life of the loan with and without this extra principal payment.