7 everywhere. 11 downtown or hipsterville.
UghRochester, everyone's given good advice. First take care of heat retention, which is insulation and not leaving your doors open, especially refrigerator. Next, manage your space -- don't heat the whole place up, because it's not worth it. If you can manage to create a smaller space where you can trap heat (whether it be a room or a sleeping bag), then small heat sources like an electric heater or heating pad can work well. Even a hot water bottle works. The trick to saving money is being efficient. The oven is a great source of heat, but I would suggest to use it only if you're also going to heat or cook food with it. Blankets, towels, clothes, and yourself can be warmed with many things, including electronics, heat from the stove (but be careful of steam -- you don't want to get wet), lamps, etc.
Use clothing to help keep yourself warm. If your hair keeps your head warm, then great. Otherwise, hats (I can see you in number 9 or 10), and definitely socks. Those are the two main things you want to keep in good condition. I cannot stress enough the importance of good socks. Not only are you on your feet a lot and good socks can help good shoes in terms of support, but if your feet are warm, you will feel warm. It's worth it to buy thick socks. Hell, if you don't care, those fluffy plushy house socks actually work quite nicely. Alternatively, house slippers.
You know, if you wanted to, you could always try stealing electricity from other places. Various ways to do that -- stay out longer, at coffee shops, libraries, schools... keep yourself warm on someone else's heat (the latter two also tend to offer free computer/internet use). Invest in rechargeable batteries (if you have any battery-operated devices) and use aforementioned places to charge them.
Well, that last bit is a touch facetious. But still notable.