Heating Degree Days and Cooling Degree Days are measures of temperature used by virtually every electric utility. However, the concept of Degree Days actually predates the existence of utilities. Degree Days were invented by Sir Richard Strachey in 1878. Strachey was a member of the Meteorological Council to the Royal Society placed in charge of investigating a famine in India. Strachey’s inquiry led him to invent the concept of Degree Days as a way of estimating the amount of heat necessary for growing crops. Degree Days were shortly adopted by utilities for estimating energy demand based on weather and they are still used for this purpose today.
To put it in perspective: the basic process we use for analyzing weather was invented the same year that Thomas Edison invented the phonograph. Audio technology has successfully progressed over the last 130 years, but somehow weather analysis has not. I'm honestly not sure if it would be possible to find another household/commercial/industrial practice that has persisted as long; everything we did in the 1800's has been replaced by new and better technologies... but utilities are still using Degree Days. And I don't believe this is a case of "if it ain't broke don't fix it." Degree Days are genuinely detrimental for utilities and I'm prepared to explain why.
Read for my next post to learn about a modern approach to weather data.