<prompt> Human: I own a home in one of US expensive real estate areas. Its currently worth a little over 1,000,000. I currently have almost exactly 600K left on my mortgage with APR of 4.125 I have 27 years left so that means Im going to be paying about 660K in interest. Ive been looking at remortgaging and I can see the appeal of both 20y fixed and 30y fixed.20y fixed: I can get one at 3.38 APR. This over 20 years I would be paying approx 416K in interest. Thats 250K less than my current mortgage. My monthly payment will go up with 500, which I can afford to pay. But of course this is 500 that I wont be able to invest.30y fixed: I can make my montly payment go down with 400 by remortgaging to a 3.62 APR. My total interest payed over the entire 30years would hardly change compared to now. But this would leave me 400 every month to invest in something that could potentially earn more than 4 interest.It seems that both situations are attractive but for different reasons. What would be the best thing for me to do?Assistant: Unless you refinance to a 15, I really dont see what you are going to save over just making extra payments to pay it off earlier. 600k is a lot of interest. Can you find something to buy to trade down? With that much equity you could find a 400k house, and pay cash, and invest your entire house payment. Human: There is no 400k houses in the SF Bay Area. My home is about as cheap as they get. Im not complaining though, Im just trying to find the optimal approach.Im curious about you saying that Im not going to save over just making extra payments.My current mortgage vs to refinance to 30y with 400 cheaper payment and paying down 400 faster saves me quite a lot of money right?  <response>: Not true, I saw a very roomy refrigerator box on the side of the high way going for 399k. 