October 30, 1999, Revised August 29, 2007
"Re your column on 'How Much Is a 1/4 Percent Rate Reduction Worth?', as
a mortgage broker of 20-years standing, I want to add a simple
explanation that I always give to my clients. On a $200,000 loan, a 1/4%
lower rate reduces the monthly payment by about $33 a month whereas 1.5
points amounts to $3,000. Dividing 3,000 by 33 you get 91 months you
have to wait to break even…Most people see the light and opt out of
doing it."
Break-Even Periods Based on Rules of Thumb Can Be Far Off the Mark
The broker quoted above is referring to a case where a borrower who had
previously agreed to pay 6.75% on a 30-year fixed-rate mortgage, was
offered 6.50% for an additional 1.5 points. The broker divided the
additional $3,000 in points by the $33 saving in the monthly payment
from the lower rate to determine a breakeven period of 91 months. What's
wrong with that?
Plenty! First, it ignores differences in the loan balance in the two
cases. The lower rate mortgage amortizes faster -- the borrower owes
less after any period. On a $200,000 loan, for example, the borrower
with a 6.50% loan owes $178,807 after 91 months where the borrower with
the 6.75% loan owes $179,611.
Second, the back-of-the-envelope method ignores the time value of money.
Money paid today is worth more than money paid in the future. The $3,000
discount paid upfront, for example, would have earned about $2,000 in
interest if it had been invested at 7% rather than being paid out as
part of the mortgage transaction.
Third, the broker's approach ignore taxes, which affect the answer
because points and interest are treated differently by the tax code. On
a home purchase transaction, points are fully deductible in the year the
loan is made whereas interest payments are deductible in future years as
they are paid.
Proper Calculation of the Break-Even Period
The breakeven period is the period over which the cost to the borrower
would end up the same whether the borrower took the high points/low rate
mortgage or the low points/high rate mortgage. To calculate it properly,
the cost must includes points, monthly payments, the lost interest
earnings on both the points and the monthly payments using the
borrower's investment rate, less tax savings and less the reduction in
the loan balance.
Charles Freedenberg and I have developed a rate/point calculator that
takes account of all the factors that affect the break-even period. It
is very simple to use. Just indicate whether the transaction is a house
purchase or a refinancing, and enter the loan amount, term, income tax
bracket and reinvestment rate. For FRMs, the calculator is 11a.
The Break-Even Period for Paying Points on Fixed-Rate Mortgages. The
comparable version for ARMs is 11b.
The Break-Even Period for Paying Points on Adjustable-Rate Mortgages.
The income tax bracket is the rate you pay on the last dollar of income
you earn, sometimes referred to as the "marginal tax rate". If you pay
taxes but don't have a clue, enter "28"; any error will be small.
The reinvestment rate is important. To get the lower rate, you pay
higher points, and the money used to pay those points could be invested.
Similarly, to get lower points you pay a higher rate, and the money used
to make the larger monthly payments could be invested. If your spare
money is held in a money market fund on which you earn 4% or 5%, you
should use that figure. If you own a stock portfolio that returns 15%,
you will want to use a higher reinvestment rate, although probably not
15% because that return is far from a sure thing.
When you click on the "Compute" button, you will get the break-even
period calculated before and after-taxes. In both cases, the calculator
shows you the costs on both loans over the period to break-even. The
costs consist of the sum of the monthly payments, the points, and the
interest on the payments and points, less the increase in equity from
loan repayments.
In the after-tax case, tax savings are deducted from the mortgage
payments and the points, and interest is calculated on the net figures.
The total cost of the two loans will seldom be exactly the same to the
penny over the break-even period. The breakeven month is the month when
the total cost of the low interest rate loan flips from being above that
of the high interest rate loan to being below.