Do the analytics. Take an amortization schedule. Plug in all your numbers from the loan start date, interest, loan amount and calculate, then amortize. Then take a portion of your equity. Say 40k. Pay 40k to your amortized loan, on paper by subtracting the 40k from your current amortized balance. Find the number of the month that is associated with the new balance you calculated. Sum the total of the interest only between your old balance and new. Then take the 40k and multiply it by the simple interest rate for the HELOC. You’ll arrive at an annual rate that you’ll divide by 12 to get your monthly interest payment to the HELOC. The difference between the amortized int. you are scheduled to pay and the simple int. that you pay will be substantial enough to off set whatever tax benefits you perceive to be more beneficial.