Here’s the numbers:
Your original loan of $417k at 3.75% will cost you a total of $128,853.17 in interest over 15 years. Since you said you paid off $7k in principal, then that would mean you paid off $5,180.01 in interest. So if you continue on this loan, you have to pay the remaining $123673.16 in interest.
If you refi today with the remaining balance of $410,049.94, your total interest over the next 15 years would be $108,582.78. That’s a saving of $15090.38 over the next 15 years in interest. So, lets say your prior loan cost you $6k, then the saving on interest – prior loan cost is $9090.38. This is not counting the monthly payment saving.
Prior loan’s monthly payment is $3,032.52 and the new loan’s monthly payment is $2,881.29. That’s a saving of $151.23/month or $27221.40 over 15 years. Add this saving with the $9090.38 in saving on interest and your total saving would be $36311.78. However, the down side would be you paying 4 more months.
I didn’t count the ~$5k you already paid in interest because you already paid for that. My calculation is strictly on whether you should refi right now if you can get 3.25% at no cost. For a saving of ~$36k, I think you should totally do it. However, I’ve missed the fact that the last 4 months without mortgage will offset you $11525.16. So your real saving is ~$25k, not $36k. Still worth it I think.
