Since when is computing power measured in watts? Put ten pentium IV chips under load and you waste a kilowatt but get ten times less computing crunch than a single 10 watt iPhone CPU.
The Terafab is pitched as a vertically integrated 2 nm chip foundry producing a terawatt of compute annually for satellites, cars, and robots. The plan involves a lot of hubris, as there are daunting capital and execution risks with Musk having a mixed record on manufacturing scale-ups.