Well, it's not so much energy by itself, but an energy gradient.

In simple terms, having electricity is great. In contrast, oceans full of water at a balmy 20C have lots of heat energy, but you can't really use it, if there's no gradient.

See the second law of thermodynamics.

Or in other terms: you want electricity and a way to get rid of waste heat, like being able to radiate into outer space.