‹ Consumption & Efficiency

Commercial Buildings Energy Consumption Survey (CBECS)

Maps

U. S. Census Regions and Divisions:

U.S. Census Regions and Divisions Map

U. S. Climate Zones for 2003 CBECS:

U.S. Census Regions and Divisions Map

U. S. Climate Zones for 1979-1999 CBECS:

U.S. Census Regions and Divisions Map

How are U.S. Climate Zones defined?

The CBECS climate zones are groups of climate divisions, as defined by the National Oceanic and Atmospheric Administration (NOAA), which are regions within a state that are as climatically homogeneous as possible. Each NOAA climate division is placed into one of five CBECS climate zones based on its 30-year average heating degree-days (HDD) and cooling degree-days (CDD) for the period 1971 through 2000. (These climate zones have been updated for the 2003 CBECS. All previous CBECS used averages for the 45-year period from 1931 through 1975.)

A HDD is a measure of how cold a location was over a period of time, relative to a base temperature (in CBECS, 65 degrees Fahrenheit). The heating degree-day is the difference between that day's average temperature and 65 degrees if the daily average is less than 65; it is zero if the daily average temperature is greater than or equal to 65. For example, if the average temperature for a given day is 40 degrees, then the heating degree-days for that single day equal 25. Heating degree-days for a year are the sum of the daily heating degree-days that year.

Similarly, a CDD is a measure of how hot a location was over a period of time, relative to a base temperature (65 degrees Fahrenheit). The cooling degree-day is the difference between that day's average temperature and 65 degrees if the daily average is greater than 65; it is zero if the daily average temperature is less than or equal to 65. For example, if the average temperature for a given day is 80 degrees, then the cooling degree-days for that single day equal 15. Cooling degree-days for a year are the sum of the daily cooling degree-days for that year.

There are 359 NOAA climate divisions within the 50 U.S. states. Boundaries of these divisions generally coincide with county boundaries, except in the western U.S., where they are based largely on drainage basins. For a map of all the NOAA climate divisions in the U.S., see http://www.esrl.noaa.gov/psd/data/usclimdivs/data/map.html. For individual state maps that show the NOAA climate divisions by county, see http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/CLIM_DIVS/states_counties_climate-divisions.shtml.

Each building in the CBECS is assigned a CBECS climate zone based on the 30-year average (1971-2000) HDD and CDD (base 65 degrees Fahrenheit) for the NOAA climate division in which the weather station closest to the sampled building is located.

The ranges of HDD and CDD used to determine climate zones are:
Climate Zone Cooling Degree Days Heating Degree Days
1 Fewer than 2,000 More than 7,000
2 Fewer than 2,000 5,500 to 7,000
3 Fewer than 2,000 4,000 to 5,499
4 Fewer than 2,000 Fewer than 4,000
5 2,000 or More Fewer than 4,000

This Excel file provides the CBECS climate zone for each U.S. county. Usually, there is only one climate zone per county and the mapping is straightforward. However, in some of the Western states, the NOAA climate divisions (on which the CBECS climate zones are based) are defined more by drainage basins than by counties, and so sometimes there is more than one climate zone per county.


Specific questions on this product may be directed to:

Joelle Michaels
joelle.michaels@eia.gov
Survey Manager