Why is heating?

So, I want to make an early start save with nothing but horses for the beginning, and I want to have energy management on. Or at least wanted to until I realized heating is a part of it, because the horse dumper wagon cannot keep up with the heating plant.

Why is heating not a separate setting? It's a different building category and everything, a completely different system, it feels like it should be toggleable independently from power management.

Does anyone know why is it like this?