April 2014

Dustin Tripp

Like many of you, I’m certainly glad to see Spring finally arrive.  The cold winter months resulted in most residential services consuming record energy consumption resulting in higher electric bills.  I would like to take this opportunity to help explain why many residential and business services experienced higher than average energy consumption and subsequent higher electric bills in the first few months of 2014.

Utilities consistently monitor temperatures to help determine the necessary demand for energy and heating degree days is an index that quantifies the demand for energy needed to heat a specific structure, such as a home or business, during the winter months.  A similar index, cooling degree days, is used to help determine the demand for energy to cool a structure in the summer.

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 following is a table that shows historical values for the heating degree index in Southern Illinois for the winter months of December 2013, January 2014 and February 2014.

Heating Degree Days As Measured In Southern Illinois






% Above



% Above




5-Year Avg.

5-Year Avg.


10-Year Avg.

10-Year Avg.

December 2013








January     2014








February   2014

















As stated earlier in the article, the months of December, January and February proved to be very cold months with much colder than average temperatures.  As you can see in the previous table, the heating degree days for all three winter months exceeded both the 5-year and 10-year averages.  In addition, it is interesting to note that in 30 years of data, December 2013 was the 4th coldest December month, January 2014 was the second coldest January month and February 2014 was the coldest February month.  If you combine the three winter months of December, January and February, this winter was the coldest winter in 30 years of data!

This information is helpful in understanding why most residential customers experienced significantly higher energy consumption during the winter months and subsequent higher energy bills.  The electric bills are higher than average due to the colder temperatures we have encountered, equating to higher heating degree days which required the heating systems in our homes and businesses to run longer, consuming more energy than they normally would have.  In many homes that have a combination heat pump with electric resistance backup heat, the heat pump was not able to extract enough warm air to heat the residence due to the extreme cold temperatures outside and this resulted in the electric resistance heat supplying much of the heat for the residence.  When this occurs, the electric resistance backup heat requires significantly more energy to heat the home and resulted in considerably higher energy consumption for the month. 

With Spring finally here, hopefully we have seen the worst of the cold weather for a while and we can all enjoy milder weather conditions and subsequently lower energy consumption.

See you next month and as always, "We'll keep the lights on for you."