Heating/Cooling/Growing degree-days?

Is there any data directly available from one’s own (and nearby) station about degree-days for heating, cooling, and growing?

Could one’s base temperature for heating/cooling degree-days be derived from historical data from a smart thermostat like Nest?

perhaps I could have googled it myself, but what is the definition of degree-day for heating? or cooling or growing?

https://www.weather.gov/key/climate_heat_cool for heating and cooling. Growing degree days vary bu crop, I believe … https://extension.psu.edu/understanding-growing-degree-days .

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All data is available via several sources (locally or server side) and since you have the definitions/formula’s, you could write your own script for it.
Not sure you’ll find such script out of the box.

hmm to that sounds like a not too useful value. Wouldn’t it be better to just monitor your electricity usage? At least that seems the idea behind the values… give an estimate of how much energy you use at a given day. But you have the exact value when you read your meter.
Growing degrees day might be useful, but probably depends too much on the particular crop so that’s a value you should expect to be directly available from a weather station.

The NOAA style reports generated by Weewx include heating and cooling degree days, and allows you to specify a custom baseline temperature.

If you setup Weewx to listen to the UDP packets transmitted on your local network you would be able to see these values for each day


Energy usage is an entirely different metric, one that I’m trying to correlate to heating/cooling DD - with a longer-term goal of catching changes in system efficiency, indicating a possible maintenance issue. Much of the heating/cooling stuff out there is tied to nearest airport WSOS and is only granular down to whole days.

Growing degree-days are relevant to tracking phenology, and not specific to a given plant. Usually measured above 5 degrees Celsius.

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after reading the provided link I got the impression that heating/cooling DD was a very crude measure of how much energy is needed for heating/cooling. Very imprecise. Now if for a specific building you are able to find a correlation between H/C-DD and energy consumption, that’s great (it will be different for a different building), and once you have that, there might indeed be a maintenance issue when it doesn’t follow that correlation any longer.
The link to the GDD above mentioned that for corn you need to use 50F and for Alfalfa you need to use 41F so it is very much dependent on the kind of crop.

HDD/CDD are almost certainly not a linear relationship to energy use, because your insulation performance also comes into play… But at some point once you exceed a certain amount of hot or cold, the system can’t keep up. It’s also useful for predicting demand and timing.

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Yes, the mean of the high/low temp is the standard way to determine GDD, and it is a number that is reported by the NWS (and no doubt by similar offices in other countries). With that said, the precision of the growth model (or insect emergence, etc.) can be improved by using the average temp using many data points throughout the day. Another problem with using NWS average temps is that often the weather station can be miles away from the field of interest.

Stupid noob question (and to see if I want/should incorporate H/CDD & GDD into my project)… but…

Are we talking predictive or historical? Do you want to know what the DD was yesterday, etc… or what it will be tomorrow, etc?