I used to do ur mistake... forget about resistance...
use P=VI ... when there is a higher Voltage there HAS to be a lower current. THE POWER IS THE SAME, its not changed. so when one is increased, the other decreases.
The more the current, the more there is heat loss. so we want a high voltage, which will cuz the current to be less and so less heat lost. but the same power will be given.