When it gets really, really cold....

[Leftfield]

....a lot of folks will "bite the bullet" and not turn the heat up only to find that their plumbing will burst.   At that point, the plumbing bill will most likely be much more than the extra amount the utility bill could be and they stand a good chance of doing without water for a good number of days.

More importantly, if you have neighbors who are elderly and/or frail, please check up on them.  I keep thinking of that poor guy who fail on his heater grate and died from severe burns.