Although most electricity is used in summer months (for air conditioning), in the 2016-2017 winter months, December and January were actually the two highest months of usage.
In the 2016-2017 winter season, residents of Connecticut, Massachusetts, New Jersey, New York, Pennsylvania, Illinois, Michigan, Ohio, Delaware, DC, Maryland and Texas paid the highest electricity bills in December and January. Although the magnitude differed in each state, the data clearly shows that December and January were the months where residents paid the most money on electricity.
Why is that?
It’s not because of the number of days. The data used in these graph was normalised so that the number of days in each month would not automatically mean lesser or greater amount of energy used.
Instead, it’s because the weather was a little colder. In almost every state, the average temperature in December 2016 was significantly colder than the average temperatures in December 2015 and 2014. The average temperature in January 2017 was more similar to the temperatures in 2016 and 2015. This can be seen on the graph with December 2016 being one of the coldest, and with a gradient much more gradual to January than other years.
Second, one of the largest winter storms that hit the US of the 2016-2017 winter - Helena - affected almost every state in this data set. The storm happened from January 5th to 8th, which could explain the increase in energy use that month. It may not have been the coldest January for these states’ residents, but the states were covered in snow. The snow may have left some people at home during the workday, increasing their energy usage at home, and the snow may have left some needing to power machines to clear the areas around their houses. As for other years -- winter storms tend to hit in January.
Finally, it’s also possible that these months had higher energy usage because of the holiday season. This means there are more people at home who have taken one or two weeks off to celebrate and, as a result, use more energy in the day than they normally would. Parties and other celebrations would likely leave residents with higher electricity bills, especially with lights and decorations which have been shown to use a lot of energy.