In: Finance
Calculating interest paid over the life time of loan
To find the interest paid over life time of loan, we need to find the monthly payment of loan
Loan = $180000, No of months of loan = 12 x no of years of loan = 12 x 10 = 120 months
Monthly rate of interest = APR with monthly compounding / 12 = 6% / 12 = 0.50%
We can find the monthly payment of loan using PMT function in excel
Formula to be used in excel: =PMT(rate,nper,-pv)
Using PMT function in excel, we get monthly payment of loan = 1998.3690
Total amount paid over life of loan = Monthly payment of loan x no of months = 1998.3690 x 120 = $239804.2800
Total interest paid over lifetime of loan = Total amount paid over life of loan - Loan = 239804.2800 - 1800000 = $59804.28
Hence Total interest paid over lifetime of loan = 59804.28
Calculating Interest saved
Additional monthly payment = $150
New monthly payment = Monthly payment + Additional monthly payment = $1998.3690 + 150 = $2148.3690
If the monthly payment is increased, then no of months to payoff the loan will be reduced. We can find the no of months of payoff loan with new monthly payment by using NPER function in excel
Formula to be used in excel: =NPER(rate,pmt,-pv)
Using NPER function in excel, we get get no of months to payoff loan = 108.8454 months
Total amount paid over life of loan = no of months x monthly loan payment = 108.8454 x 2148.3690 = 233840.0832
Total interest paid over life of loan = Total amount paid over life of loan - Loan = 233840.0832 - 180000 = 53840.0832
Total interest saved over life of loan = 59804.28 - 53840.0832 = $5964.1968
Answer: $5964.1968