I wonder is Apple using the Tensor chip because it uses way less power than the nVidia chip in the same application?
No. A TPUv4 rack requires more water flow than a fire truck pump can deliver to keep the system cool enough. A TPUv5 rack likely requires as much or more power and water cooling. These are racks and racks of massively hot supercomputer chips that Apple is using for ML training. The electric power bill for training just one of the largest LLM models can run into many millions of (USD) dollars.