First it is important to understand a HELOC. The term home equity line of credit is not interchangeable with the term "second mortgage." A "first" or "second" mortgage only refers to the loan's claim position, not its terms. HELOCs are often referred to as "second" mortgages because there is usually another mortgage against the property when they are taken out. If one were to default, the lender in second position would not see any money until after the lender in first position had been repaid. However, it is possible to have a HELOC in first position if there is no other mortgage on your home when you open a HELOC or you use the HELOC to pay off your first mortgage.
Let's take a look at how a HELOC could work as a first mortgage. For our example, let's take a $200,000 30-year conventional loan at a fixed interest rate of 5.50%. For this loan the payment would be approximately $1,130 per month (roughly $900 interest and $230 principal in initial years). Total interest paid over the 30 year life of the loan would be roughly $208,000; more than the original loan. As we know, an amortized loan is mostly interest paid in the early years and mostly principal paid in the later years.
Currently interest rates on HELOCs are 3.00% or less in some cases. The interest rate of a HELOC is a simple interest calculation and is not amortized over a set period of time. Therefore, each payment toward principal reduces the next month’s interest expense. The interest rate is variable so if interest rates rise, the interest charged will increase and vice versa.
For example, a $200,000 home equity line of credit at 3.00% would require a minimum interest payment of roughly $500 per month; almost half of the interest paid on the convential 30-year loan. If one continues to make the same $1,130 payment each month toward a HELOC, which would result in a $630 payment to principal each month. If we assume the interest rate stays at 3.00%, the loan could be paid off in roughly 19 years and total interest paid would be $65,000; much less than the total interest paid on the same convential loan.
Even if interest rates increased by .25% each year (HELOCs have variable interest rates), the loan could be paid off in approximately 23 years with total interest paid of roughly $143,000; still much less than the original total interest amount on a conventional mortgage.
While converting a first mortgage to a HELOC may not be the best option for everyone because of the variability of interest rates; in an environment of low, steady interest rates a HELOC could be a great opportunity to pay down a mortgage more quickly versus a coventional 30-year mortgage. A HELOC is most attractive if a homeowner makes extra payments toward principal, which in turn reduces the monthly interest expense.