Kind of counter intuitive. Wouldn’t the GPU be more efficient at rendering graphics than the CPU? For laptop models with dedicated GPU just use the integrated one on battery but ALWAYS prefer Metal GPU rendering to software.
We’re not talking about wattage, but energy consumption. I.e. a single core working at its max for 5 seconds uses more power than three cores working for one second. It’s a question of efficiency, not how many cores are working at once.