You can use a dimmer, but a thermostat is alot better. I've been using a dimmer, if I wasn't home all day though, I would've bought a thermostat a long time ago. Dimmers require you to check in on the temp almost every hour, so unless you're able to do that, get a thermostat.

I just ordered mine off this website, which has a pretty good price and they even add discounts.

http://www.bigalsonline.com/StoreCat...its=12&offset=