I love Minnesota. Just got my $376 utility bill due to the -15 weather for a few weeks straight - and we kept our house at a balmy 64 degrees.
My coworker has a high end new construction bigger than mine and keeps it at 72 for his baby, and had a smaller bill (way better insulation than my 1962 house). My other coworker has a smaller house than me and was pushing $500, but his windows are practically falling out (not really, but they're drafty).
So, size does matter, but insulation and window quality matter more.
As far as electricity goes I used to have a chest freezer from the mid 80s. I got rid of it and my electric bill dropped like $20 / month. That thing was a guzzler apparently !
Also. Heated floors make the wife happy, but they come at a price...