Heat/cold degree days and Chill hours

Explanation

Heat Degree Days

You may have a thermostat that makes your heating come on when the temperature falls below a threshold. Cumulus calculates the time that the temperature is below that threshold and reports it as 'Heat degree days' using the unit of days. So if for each day of November, there was just one hour below the threshold, the total for the month would be 30 hours reported as 1.5 days.

Cold Degree Days

You may have a thermostat that makes a cooling system come on when the temperature rises above a threshold. Cumulus calculates the time that the temperature is above that threshold and reports it as 'Cold degree days' using the unit of days. So if for each day of June, there were 3 hours above the threshold, the total for the month would be 90 hours reported as 3 days.

Setting the threshold

Within the Configuration menu, there is a NOAA Setup option. The picture shows just parts of the setup screen. It shows the units you have selected to use in your implementation of Cumulus and allows you to specify the two thresholds. Cumulus stores your selected values in Cumulus\Cumulus.ini.

CAUTION: Think carefully, about what threshold to use. If you later change the threshold, only subsequent calculations use the new threshold. All retrospective calculations remain based on the old threshold, so values shown for a month or a year with a threshold change will be rubbish, and need to be manually recalculated.
Sfws 07:42, 29 November 2012 (UTC)