Whether or not to pay down extra principal each month is a complicated question, and one that doesn't have a universal answer by any means. For the purposes of this discussion, we'll assume that an extra payment fits in your budget. Otherwise, the question is a bit moot.
Paying down principal has two primary effects. First, it takes money out of your pocket. Second, it increases your equity. Increasing your equity has the effects of reducing the interest you pay over the life of your loan and increasing your borrowing power. We'll go backwards through these effects this time around.
The borrowing power I'm referring to here will usually take the form of a home equity line of credit (HELOC). If you make a larger down payment, your monthly expenses can be lower, which can increase your borrowing power for a new loan, but if you're just getting a mortgage, chances are you're not looking for many other new loans. (Indeed, you shouldn't be, as new loan credit inquiries can negatively affect your credit score! Wait for your mortgage to be finalized before looking at car loans, for example.) The only thing I would use a HELOC for is an emergency fund. It's a great way to be able to pay down principal and still have access to that money in a pinch. If the pinch comes and you don't already have a HELOC, you're unlikely to be able to get a HELOC, so it's important to plan ahead. HELOCs are usually restricted to whatever equity you've built beyond 20%, so that your combined LTV remains at 80% or less. They also usually require a recent appraisal, so even the no-fee HELOCs aren't entirely cost-free to set up.
To me, though, this benefit of paying down principal isn't a major selling point, as evidenced by the fact that I do not have a HELOC. For emergency funds beyond my cash on hand, I would rely on loans from my family. I haven't formalized that line of credit in any way, and maybe I should do so rather than taking it for granted. At the same time, I can make sure my family knows that I would be there for them, too.
I view principal reduction as an investment that returns a savings in interest payments. Unfortunately, the rate of return on that investment isn't always just the interest rate of your mortgage. I included a simple calculator in my post on your
effective mortgage interest rate, but that doesn't give a complete picture of your investment.
First, just as in my discussion on
S&P 500 growth, values were not inflation adjusted. When it comes to the returns of the S&P 500, you have to subtract the inflation rate to get an
inflation-adjusted return (approximately, anyway). Your mortgage works much the same way except that inflation helps debt, so you get to subtract the inflation rate from the interest rate you pay and get an inflation-adjusted interest rate. You get a benefit now (the home) and pay for it with less and less valuable dollars. Not a bad deal for the purchase, but it lowers the rate of return on principal payments. For the default values in the calculator above, the effective interest rate is 3.75%. After adjusting for inflation by subtracting
3.3% (though recent inflation has been lower), you're left with a nice low 0.45% inflation-adjusted effective interest rate.
Second, paying down principal now takes off interest from the very end of the loan. Your minimum payment doesn't go down and you can't readily access that money except through a HELOC. It is definitely a long-term investment, and the rate of return is locked for that entire period. It's similar to buying a multi-year CD with a rather - even ridiculously - low rate, given the current interest rate environment.
Third, paying down principal really shows the nature of compounding. Every payment that goes by, the principal you pay down saves you one fewer compounding of interest. Take a look at a monthly amortization schedule (
my favorite calculator). You'll notice that the principal you pay goes up each month, while the interest paid goes down. Where you are in the schedule depends entirely on the principal outstanding, so to move up the schedule by a month (and in effect take a payment off the back end), you just have to pay the principal for the next month ahead of time. Thus, the extra payment required to gain a month goes up each time. The rate of return doesn't go down, but the time horizon is shortened and the compounding reduced. If that shortening of the time horizon is your goal, there are definitely diminishing returns.
As mentioned above, paying principal takes money out of your pocket. Whether or not paying principal is a good investment really depends on which pocket the money comes from. If it's coming from a cash account, chances are good that you will get a larger return by eliminating interest. If you are paying extra principal instead of making an IRA or 401(k) contribution or otherwise investing, then you are missing out on what is very likely to be a higher return in the stock market. Remember that it is important to compare inflation-adjusted rates to each other, and non-inflation-adjusted rates to each other. Mixing and matching is not a valid comparison.
Basically, as near as I can tell, prepaying principal doesn't make financial sense unless mortgage interest rates are over ten percent or so. I don't think many people today would pay down their mortgage if it weren't for the psychological benefits. Being in debt just doesn't feel very good - especially when it's tens or hundreds of thousands of dollars and can result in being homeless. Conversely, there's no feeling quite like
knocking another month off the end of your mortgage. It's also a lot of fun to reduce your principal by the first $1,000; the first $10,000; the first $100,000 (I imagine). I'm also really looking forward to the day (soon, I think!) when my various investment and cash accounts could pay off my mortgage if I liquidated them. That would mean I could pay off the house if I had to, significantly lowering my monthly expenses so that I could live off a minimum wage job, for example. However, when I get close to the end of my mortgage, I imagine that I will pay it off simply for the monthly cash flow improvement, whether I need it or not.
In the end, I pay a
couple hundred extra each month despite the logic behind investing it instead. I guess that's the price I put on the psychological benefits above. Pretty cheap therapy, actually.
