The energy has to go somewhere so they are using it for SOMETHING instead of just heating up a giant resistor and venting it into the air. This is because deman

The energy has to go somewhere so they are using it for SOMETHING instead of just heating up a giant resistor and venting it into the air. This is because demand is so variable. This is the equivalent of storing water from a river in a reservoir when you aren't watering your field. Sure, some of it evaporates but you aren't just letting it run into the ocean.