Comparing Metro Phoenix
Climate
Description: Degree days estimate the amount of heating and cooling needed to maintain a comfortable interior environment. Hot days, which may require the use of energy for cooling, are measured in cooling degree-days. Cold days are measured in heating degree days. In order to calculate cooling degree days, a reference temperature of 65° F is subtracted from the daily mean. Heating degree days are calculated by subtracting the daily mean from the 65° F base.
Rationale: Increases in the number of degree days lead to increased energy demand to heat and cool building interiors. Higher energy requirements have financial impacts for individuals and businesses, and degree days are used to model energy budgets to forecast energy consumption and project operating costs. The link between degree days and energy demand has indirect impacts on air quality. Greater demand requires increased production, yielding emissions from combustion. As a result, certain air pollutants, such as carbon monoxide and nitrogen dioxide are emitted and threaten regional air quality. Indoor air quality is also impacted when structural changes are made to buildings in response to degree days and energy forecasts to control the flow of air and keep external air outdoors. Air infiltration is then reduced and indoor quality can be reduced. All of these factors influence the sustainability of the place. Cities with a high number of degree days may have larger financial expenditures associated with energy consumption and may also need more stringent air quality controls to prevent pollution.
The graph shows the total number of degree days in 2006 for each comparator city. San Jose is not included in this data because it is not monitored separately from San Francisco. Phoenix has a comparatively moderate to high energy demand; less reliance on ambient energy than Denver and Salt Lake City, but more than Atlanta and San Diego. The desert environment of Phoenix requires more summer cooling than all other cities. San Diego’s relatively low energy demand indicates it may be the best example of sustainable energy usage. Data for the degree days by city reflects the energy demand of the city for 2006. The data source is the cities’ one weather service forecasting office, which represents the cities’ climate.
Source: Decision Center for a Desert City using records from the National Weather Service Climate Prediction Center, Degree Days Statistics by City, reported from the city's National Weather Forecasting Office. Available Online at http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/cdus/degree_days/.
