I think you’d first have to have a biological explanation for how they can fly before you determine how much energy it takes.

Physicists have actualy calculated that for human-powered flight (ignoring the magic/tech), a 70kg superhero would need to generate roughly 100-200 watts of continuous power just to hover, and exponentially more to achieve those ridiculous accelerations we see in movies - you’d need caloric intake that would make The Flash look like hes on a diet.

It doesn’t take any energy to fly, if you’re made of helium.