Is daily usage of an oven the reason my power bill is so high?

My power bill is extremely high for my apartment, and I can't really pinpoint a reason. We live in Florida, but keep the air temp. on 85 during the day and 78 at night for the sake of saving energy (and it is HOT in here!) We keep lights off whenever we can and unplug appliances/ turn them off when they are not in use. However, a new room mate moved in recently and he cooks with the oven and stove daily, and he sometimes forgets to turn it off for a while. Could this be the reason it is so high? Does the use of an oven/stove daily increase my power bill a lot? (It wasn't as high before he moved in, even during the heat of the Summer)