Two factors are at play on your bill; the amount of energy used and its cost. The following example is based on natural gas but electricity would be similar.

This Year Last Year
Usage in Therms 113 72
This winter is 13% colder than Normal.
Gas cost/Therm $0.718 $0.420
Average gas prices have more than doubled
Billed $81.13 $30.24
Your bill will be the higher than it has been in the last 5 years

 

Last year was warmer than a Normal* winter; in fact it was 72% of Normal in December 2012 and January 2013.

So if in a Normal year you use 100 Therms of natural gas, last winter you used 72. This was when the price of natural gas was about $0.420/Therm.

Now consider this December 2013 and January 2014 winter that is 13% colder than Normal.

So you will use 113 Therms. This is when the price of natural gas is about $0.718/Therm.

 

*a Normal winter is an average of 20 winters