Energy statistics for 2011
 
I perform many audits throughout the year, keeping the data for later analysis. Here is what I've come up with from the audits performed in 2011:
 

2011 Statistical Data 

Square feet

Cubic feet

Leakage (CFM50)

Gas BTUs

kWh BTUs

Total BTUs

HDD

CDD

Stories

Occupants

N-Factor

Year Built

 Averages

3,020

28,517

3,284

108,252,517

56,507,201

122,607,026

5,571

755

1.7

4

20

1979

 Highs

8,000

80,000

12,115

384,000,000

227,895,100

424,504,986

6,709

1,334

3

15

25.8

2006 

 Lows

1,100

8,800

850

0

0

0

4,003

24

1

2

13.3

1930

  
Square feet: The amount of conditioned floor space for a building
Cubic feet: The result of the square footage and the height of every room
Leakage (CFM50): The amount of leakage in cubic feet per minute when the house is depressurized to -50 Pascals
Gas BTUs: The total amount of BTUs consumed as a result of burning gas
kWh BTUs: The total amount of BTUs consumed as a result of using electricity
Total BTUs: The total amount of BTUs consumed from both gas and electricity
HDD: Heating Degree Days (environmental conditions when heating is necessary)
CDD: Cooling Degree Days (environmental conditions when cooling is necessary)
Stories: Amount of levels of a home
Occupants: Total people occupying a home full time
N-Factor: Environmental conditions affecting how a home is exposed to the elements like wind, shade, and temperature swings
Year Built: Year in which the home was built
 
Using this data, we can compare homes we audit with averages to determine how far from the average a home might be and make recommendations accordingly. In addition, we can use this data for some much more. For example, look at the chart below. Add up all of your utilities (gas and/or electric) for the past year and plot that on the graph, intersecting with the square footage of your home. The solid line indicates the averages based on these parameters. If your intersection is not close to the line, you can most likely benefit from an energy audit.
Utility cost averages by square footage