I am guessing that it is a 220 unit. If it wasn't, you could buy a Kill-A-Watt meter and check for yourself.
At the laundromat, they claim that a dryer stuffed full of cloths drys just as fast as one with a small amount of cloths, but I don't believe that. I think the hot air need to circulate in order to dry the cloths.
When I had my own dryer, I would usually put it on medium heat because my shirts would shrink if I used the high setting. After a few drying on high, my baggy t-shirts would start to look like bikini tops, and that is something you don't want to see me in.
Theoretically, it should take the same amount of heat energy to dry your cloths whether or not it does it fast or slow, but there are other factors. The greater the difference in temperatures the faster the change. If you have it on high, your cloths will dry faster, but most of the heat will go out the exhaust. If you use a low heat setting the fan motor will be on longer which uses up electricity. There might also be something like humidity saturation of the air, or whatever it is called.