I'm pretty amazed at how much more our electric bill is for the month of December. It was an extra $25 and the only thing we did differently was do a few Christmas lights.
You live in Michigan, right...? Gets dark sooner, stays dark longer, you use more home lighting, if you have outdoor security lighting, it stays on longer. Your furnace motor is electrical, the furnace runs more, right? You don't want to go out someplace to eat, meaning your stove and microwave get used more. Instead of being outdoors mowing your lawn, you sit inside at your computer and use more juice than normally. Your fridge door, like ours, gets opened and closed more frequently. You watch more TV, most likely...need I go on?
Want to hear about a sky high electric bill? I paid one last week that was for 33 days. We have a 2450 square foot house, two gas furnaces, two fridges, one freezer, four computers, one 50 inch plasma tv that is on 20 hours a day (wife is addicted) well pump, three outdoor security lites (energy efficient type) and although we are stingy with the lighting, last electric bill was $143 with tax for 33 days.