I live in a winterized cottage on the shore of a lake in Canada, and it does get c-c-cold here. I'm probably paying about that much for the winter months here, keeping the place at 70-degrees, between electricity and propane. Yes the heat-shrink window film will help cut down on the drafts. You should also try foam insulation on all your outlets and light switches. And if you work a predictable schedule, a programmable thermostat is a good investment. Drop the temperature to 60-degrees when you leave, bring it back up just before you get home.