If you want to be accurate with your heat dial try using a kill-a-watt.
http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&qid=1372070860&sr=8-1&keywords=Kill+a+watt
Instead of using a dial position you can use watts. This is much more accurate...