I use a Lasko ceramic tower heater. I leave it on all the time, and it has a thermostat that you set. It turns on when it drops below your temp and turns off a little above your temp. My apartment doesnt have centralized air but even thought its freezing outside and in my living room, my bedroom stays nice and toasty! I definitely recommend them.

http://www.target.com/p/Lasko-Digita...e/-/A-13671463

Something like that