"Besides, I like DC better anyways; the math is easier."
My Grandfather was a mechanical engineer who did a lot of structural engineering work on the side after he retired.
One of the buildings that he did a consult on was an old factory in Huntington, Pennsylvania. I went there with him when he did an initial physical inspection.
The building had its own power grid. Originally power had been supplied from its own boiler house, but it had been hooked into the grid at some point in time.
But the mechanicals in the building had never been changed. They were all DC -- lights, motors, everything -- and a LOT of them had been made in the 1800s (judging by the plates on the motor housings) by Edison's companies.
The power grid obviously supplied AC current, but in what had been the old generating house it was transformed into DC.