Implementing Heating Degree Days

I couldn’t find any information about implementing Heating Degree Days (HDD) within Emoncms, so I thought it might be useful to share my simple method.

I simply use the outside temperature node sketch to calculate the temperature below my property’s base temperature of 13ºC and if the outside temperature is above 13ºC I set the value to zero.  This data, which I call HDM (since I’m collecting data every minute), is then passed to Emoncms.

HDD are basically the integral over time (a day) of the outside temperature below a certain base temperature.  Since I’m collecting data every minute it is sufficiently accurate to sum the values over a day and divide by the number of data points.  Clearly this is a daily average, which is already implemented in Emoncms.  So that’s it Heating Degree Days without modifying Emoncms!

It would be nice if you could change the units on the bar graph as these show as KWh and if the whole process could be calculated within Emoncms, thus allowing easy changes to the base temperature.

See here  for HDD background information.