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The passage around this formula

Because a watt is a joule per second, $\eta$ measured this way is numerically the same quantity as operations delivered per joule. That equivalence matters because it converts a throughput specification into an energy budget for a single inference: $E_{\text{inference}} \;=\; \frac{N_{\text{ops}}}{\eta}$. where $N_{\text{ops}}$ is the number of operations one inference requires. This is the arithmetic that determines whether a given model can run a given number of times on a given battery before it needs replacing or recharging, and it is why a headline TOPS figure on a datasheet, quoted without the power draw it was measured at, tells a reader almost nothing about whether a part is suitable for a battery-powered product.

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