Heating degree days is calculated by taking the average base temperature that a specific structure is normally heated to minus the average outside ambient temperature for each day of the month and then adding all days in that specific month. Many would think that the base temperature would be around 70°F but for historical reasons and the availability to compare this index over a long period of time, the base temperature is normally defined as 65°F. In order to calculate this index, assume the average outside ambient temperature for the 1st day of the month is 20°F. The number of heating degree days for the 1st day of the month would be calculated as 65°F - 20°F = 45 heating degree days. You would continue this process for each day of the month and then add all the respective heating degree days for the entire month.
The El Nino climate cycle occurs when the sea surface temperatures in the Pacific Ocean become warmer than normal. This effect typically causes the temperatures to be warmer than normal. The El Nino climate cycle occurs irregularly but averages every 2 to 7 years. The El Nino certainly appears to have contributed to the past winter months being warmer than normal. The heating degree day data from Southern Illinois for the months of November, December, January and February revealed that this past winter was the second warmest winter over the past 32 years of record.
Conversely, the La Nina climate cycle occurs when the sea surface temperatures in the Pacific Ocean become cooler than normal. This effect typically causes the temperatures to be cooler than normal. As many of you may remember, the Polar Vortex that occurred over the winter months of 2013-2014 produced the coldest winter months in Southern Illinois over the past 32 years of record.
This information is helpful in understanding residential energy consumption during the winter months. The El Nino effect helps explain why most residential customers experienced lower energy consumption during the previous winter months and subsequent lower energy bills. The electric bills are lower than average due to the warmer temperatures we encountered, equating to lower heating degree days which required the heating systems in our homes and businesses to run less, consuming less energy than they normally would have. In many homes that have a combination heat pump with electric resistance backup heat, the heat pump was able to extract enough warm air to heat the residence due to the warmer temperatures outside and this resulted in the electric resistance heat supplying less of the heat for the residence.
With winter over, I certainly hope that all of you have the opportunity to enjoy the Spring weather and look forward to the Summer months ahead.
See you next month and as always, "We'll keep the lights on for you."