About the Tool
With this tool, you can explore how Cooling Degree Days (CDD) and Heating Degree Days (HDD), which are proxies for energy used to cool and heat buildings, are expected to change under different emissions scenarios and climate models. You can customize the metric for CDDs and HDDs by adjusting the base temperature as well as selecting the entire year or a specific portion of the year for inquiry.
The underlying data are derived from daily climate projections that have been downscaled from global climate models from CMIP5 archive, using the Localized Constructed (LOCA) statistical technique developed by Scripps Institution Of Oceanography. LOCA is a statistical downscaling technique that uses past history to add improved fine-scale detail to global climate models.
CDDs and HDDs are often used by utilities and other energy sector planners to understand energy demand for cooling and heating. As California’s climate changes, historical observed climate is becoming an increasingly poor proxy for future energy demand for cooling and heating. For example, an increase in the number and magnitude of hot days is expected to increase demand for air conditioning.
What is a Cooling Degree Day?
A cooling degree day (CDD) is the number of degrees by which a daily average temperature exceeds a base temperature and may therefore require additional energy for space cooling.
The base temperature is typically 65 °F, although different utilities and planning entities sometimes use different base temperatures. The base temperature loosely represents an average daily temperature below which space cooling (e.g. air conditioning) is not needed.
The average temperature is the average of the minimum and maximum daily temperatures. CDDs can be summed over the entire year or over a portion of the year (e.g. the month of July) as a rough indicator of cooling energy used over that period.
What is a Heating Degree Day?
A heating degree day (HDD) is the number of degrees by which a daily average temperature is below a base temperature and may therefore require space heating.
The base temperature is typically 65 °F, although different utilities and planning entities sometimes use different base temperatures. The base temperature loosely represents an average daily temperature above which space heating is not needed.
The average temperature is the average of the minimum and maximum daily temperatures. HDDs can be summed over the entire year or over a portion of the year (e.g. the month of January) as a rough indicator of heating energy over that period.
Data Sources
The following list of datasets were used to create this tool. Download data visualized in the charts by clicking the Download Chart button. For more download options follow the links below.
