What is a Degree Day?
Degree days is a measure of how cold or warm a location is. A degree day compares the outdoor temperature recorded for a location to a base temperature, usually 65° Fahrenheit (F) or 18.3° Celsius (C). The more extreme the outdoor temperature, the higher the number of degree days. A high number of degree days generally results in higher levels of energy use for space heating or cooling.
Heating degree days (HDD) are a measure of how cold the temperature was on a given day or during a period of days. For example, a day with a mean temperature of 40°F has 25 HDD. Two such cold days in a row have a total of 50 HDD for the two-day period.
Cooling degree days (HDD) are a measure of how warm the temperature was on a given day or during a period of days. For example, a day with a mean temperature of 90°F has 25 HDD. Two such warm days in a row have a total of 50 CDD for the two-day period.
What is a Typical Meteorological Year?
A Typical Meteorological Year or TMY is a set of meteorological data with values for every hour in a year for a given geographical location. The data is selected to accommodate hourly data in a longer time period (normally 10 years or more). For each month in the year the data have been selected from the year that was considered most "typical" for that month. For instance, January might be from 2015, February from 2020 and so on.
What are your data sources?
Our database receives data from over 20 different datasets. These datasets include both Private and Public data sources. The data source is explicitly indicated at download and can include:
How is a Typical Meteorological Year calculated?
We cover a variety of methods for calculating an a typical meteorological year. The method is explicitly indicated at download and can include:
How are Degree Days calculated?
We follow the standard and widely accepted method of the ASHRAE to calculate heating and cooling degree days. In contrast to other providers, we use hourly values of Air Temperature for our calculation. This provides a more precise estimation.
How is Data Triangulated?
We offer triangulation services for locations with no specific data. The triangulation service is carried out across several locations in close proximity, with a minimum of three locations. Our method derives from the interpolation method known as Inverse Distance Weighting or IDW. Contrary to other approximations, we apply the algorithm to every single data point separately (e.g. temperature at 0:00, temperature at 1:00 etc.). This technique allows to interpolate data based on parameters such as distance, and prioritize data available as close as possible to your location.