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Take home point: "In fact, POWER* is a unitless measure because it is a semi-arbitrary combination of two measures with incompatible units."

*POWER = "Energy Impact."

Since the formula is

Power = ((used_us + IDLEW * 500) * 100.0) / elapsed_us

If you believe that each idle wake costs you on average the same energy as 500us of computation, then the units are compatible right?

For 10.9, POWER and "Energy Impact" appear to be the same. For 10.10 "Energy Impact" has changed.