Climate, that is outdoor temperature, affects how much home energy is consumed; consequently climate affects the cost of home energy. The measurement of outdoor temperature is expressed in units of heating or cooling degree days. Degree day is a quantitative index that reflects demand for energy to heat or cool houses and businesses.
The Climate Prediction Center of the National Oceanic and Atmospheric Administration (NOAA) collects temperature data and then calculates degree days from weather stations across the United States. The data are then weighted by population to produce population-weighted, degree data averages. These averages are reported weekly at the state, regional, and national level. The averages are also compared with population-weighted, degree data from the previous year and with a 30-year, population-weighted average.
Using weighted heating degree data, one can determine how cold it has been in a particular area. A heating degree day is the number of degrees for a particular day that the average temperature falls below 65 degrees Fahrenheit. For example, if the high temperature for a specific day was 50 degrees and the low temperature was 40 degrees, then the average temperature would be 45 degrees. That day would be considered to have 20 heating degree days (65-45=20). The larger the number of heating degree days, the colder the temperature is for that day.
Using cooling degree data, one can determine how hot it has been. A cooling degree day is the number of degrees for a particular day that the average temperature exceeds 65 degrees Fahrenheit. For example, if the high temperature for a specific day was 90 degrees and the low temperature was 70 degrees, then the average temperature would be 80 degrees. That day would be considered to have 15 cooling degree days (80-65=15). The larger the number of cooling degree days, the hotter the temperature is for that day.
NOAA prepares the following tables: Heating Degree Days Population Weighted Listing, and Cooling Degree Days Population Weighted Listing for the last three weeks and last three months (see data links under Weekly Tables).
Given the increasing danger of hyperthermia, the National Weather Service has stepped up its efforts to alert more effectively the general public and appropriate authorities to the hazards of heat waves--those prolonged episodes of excessive heat/humidity. The National Weather Service has devised the "Heat Index" (HI), sometimes referred to as the "apparent temperature." The HI, given in degrees Fahrenheit, is an accurate measure of how hot it really feels when the relative humidity (RH) is added to the actual air temperature.
In addition, the National Weather Service has developed a comprehensive collection of weather information.
Home energy affordability can be expressed as the percent of a household's income spent on home energy, which is referred to as home energy burden. Overall, the home energy burden of low income households is greater than the home energy burden for non low income households. The most recent data on home energy burden are available in the LIHEAP Home Energy Notebook for FY 2009.
The U.S. Department of Energy's Energy Information Administration publishes publishes data on energy supplies, demand, and prices in its Short-Term Energy Outlook, Annual Energy Outlook with Projections, and State Energy Data System.