What Does the OS X Activity Monitor’s “Energy Impact” Actually Measure?

I'm surprised that the author hasn't mentioned the positive effect it has had. After upgrading the OS and seeing the new menu entries I reported a number of applications that would show up as using a lot of energy and within a few releases there was a change note usually mentioning some simple fix which dramatically reduces the wake up's of the application or removing a long running animation that didn't add any value. This little menu addition has probably helped the battery life for macbook users more than any other change.

The first sentence of the article:<p>&gt; Activity Monitor is a tool that was introduced in Mac OS X 10.9.<p>Activity Monitor was introduced with OS X 10.3 (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Activity_Monitor" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Activity_Monitor</a>). And was significantly revamped with OS X 10.9 to receive the various energy related measurements.

Wakeups are a bit tricky to actively measure, because with the Power Nap feature, the actual # of wakeups triggered by a particular application is a bit trickier to measure and <i>varies based on what other activities are going on the system</i>.<p>In general, from the get go, it is a bit of a myth that you can really know how much of a power budget is a consequence of a particular application. You can get a rough sense of relative impact on the overall power budget, but even that can be seriously skewed by a LOT of factors. At best, you can get a sense of, &quot;if I sampled at the moment power stores hit a multiple of X, how often would I see the system doing something on behalf of each app that was draining power at that moment&quot;. Even that, is bloody hard to pull off, but it is your best &quot;rough&quot; approximation of what is going on.

I could have sworn I read somewhere that Activity Monitor also included GPU usage in its measurements—naturally, using the GPU more uses more power&#x2F;battery.

&gt; <i>Recent Intel hardware provides high-quality estimates of processor and memory power consumption ... But the big problem is that they are machine-wide measures that cannot be used on a per-process basis.</i><p>Would it not be possible for the OS to poll the CPU for these power consumption stats, and attribute the value returned to the currently running process?<p>Over time, I think it would be possible to see how much power the Intel CPU thinks each process is using.

Work in bootstrapping energy consumption exists in academia; for example Pathak et al[0]. The changes in 10.10.4 could be an implementation of something along the same lines, by fitting a model to the measured power consumption.<p>As comex notes in the comments on the article, there appears to be a table of weights for various features, presumably obtained by regression.<p>[0]: <a href="http:&#x2F;&#x2F;research.microsoft.com&#x2F;en-us&#x2F;people&#x2F;mzh&#x2F;eurosys-2012.pdf" rel="nofollow">http:&#x2F;&#x2F;research.microsoft.com&#x2F;en-us&#x2F;people&#x2F;mzh&#x2F;eurosys-2012....</a>

Take home point: &quot;In fact, POWER* is a unitless measure because it is a semi-arbitrary combination of two measures with incompatible units.&quot;<p>*POWER = &quot;Energy Impact.&quot;

Is there anything like this for iOS? I&#x27;d love to know the consumption of energy (and data) for all my iOS apps!

Surely we can also measure actual heat and actual electricity usage? If not per program obviously, then as a reference or benchmark or calibration.