 How much does
it cost to heat your home? It all depends on the outside temperature of the house. The
colder the outdoor temperature, the greater the heating cost. Engineers developed a method
to help homeowners calculate their heating costs. This method is called the degree-days.
The equation for degree-days is defined as:
 
DD = (65 – To) ´ N
Where
DD = degree-days
To = Average daily outside temperature
N = number of days
Note: 65 means 65º F indoor temperature
The average daily temperature in Washington D.C. for the first 5 days in February was:
| Day |
Average Temperature º F |
| February 1 |
35 |
| February 2 |
38 |
| February 3 |
42 |
| February 4 |
32 |
| February 5 |
28 |
What was the total number of degree-days for the first five days in February?
(65 – 35) ´ 1 day + (65 – 38) ´
1 day + (65 – 42) ´ 1 day + (65 – 32) ´ 1 day + (65 – 28) ´ 1 day = 30 +
27 + 23 + 33 + 37
= 150 DD
Using a similar calculation for days that the outdoor temperatures are below 65º F, we
can find the total number of degree-days for the entire year. Here are the degree-day data
for some U.S. cities.
| City |
Degree-Days |
| Atlanta, GA |
3,095 |
| Chicago, IL |
6,127 |
| Duluth, MN |
10,000 |
| Fairbanks, AK |
14,279 |
| Honolulu, HI |
0 |
| Miami, FL |
206 |
| New York, NY |
4,848 |
Marie lives in Atlanta, Georgia. The heating bill last year was $900. She has a sister
who lives in Fairbanks, Alaska. How much would it cost her sister to heat a comparable
house?
Estimate the answer:
 Less than $900
Between $900 and $2,000
More than $2,000
 
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