How to Monitor Which Apps are Energy Hogs in OS X Mavericks

With the release of OS X 10.9 Mavericks, Apple has taken great pains to incorporate new features that appreciably improve the energy efficiency of the Mac. Of particular importance to notebooks – the MacBook Pro and MacBook Air – is that by taking advantage of new technology, battery life under Mavericks can be extended considerably.

Additionally, starting with the new Intel “Haswell” processor, much of the energy-saving capabilities are major attributes of the processors themselves. Moving forward, and as Apple’s ratio of notebook to desktop Macs sales continues to rise, OS X – in conjunction with hardware – must remain heavily focused on extending battery life.

The Intel Haswell CPU

The Intel “Haswell” Central Processing Unit (CPU)

One of the ways that energy consumption reduction is accomplished basically amounts to having the power-hungry processor complete the same amount of work in less time, and maximizing the CPU’s low-power idle time. Simply put, if whatever the processor is working on does not benefit the user, either immediately or at a later time, it will be done less often, and if possible, not done at all.

App Nap – OS X Mavericks includes a new technology called App Nap that allows supported apps to consume very little energy when they are open but not being used. For example, App Nap might be used if an app is open on a desktop but is not currently being used, or if an app is hidden under other windows. App Nap completely suspends the app’s execution when this or other criteria are met, thus ensuring that the app does not periodically wake up to perform unnecessary tasks. The app wakes up automatically when the user either brings the app to the foreground or when the app receives a background event.

The Battery Status Menu showing apps that are using significant energy

The Battery Status Menu: after a couple of seconds, it reports which apps are using significant energy

The Battery Status Menu – The Finder’s Battery Status menu in Mavericks includes a related option to monitor the current status of app energy usage. These options appear on Mac notebook computers, whether or not a power adapter is connected. Applications are listed and identified as ones which are currently using “significant energy.” In effect, via Battery Status, Mavericks wags a finger at energy-hogging applications. And, yes… Mavericks has fingers.

Not seeing the Battery Status menu? Go to Settings > Energy Saver and enable it via the checkbox at the bottom of the Settings panel.

Activity Monitor – Activity Monitor is a built-in utility pre-installed in every Mac. It’s located in the Utilities folder. You can get there via Go > Utilities in Finder. It can be used to view how running apps and background processes are using various resources on your Mac, such as the processor, memory, disk, network and now, overall energy usage.

We learned above that the Battery Status Menu can indicate apps that are guilty of using significant energy. Selecting one of the listed applications from the menu launches the Activity Monitor app. Upon opening, it switches to the appropriate Energy section so that the offending apps can be easily identified and energy consumption statistics analyzed.

The Energy section of the Activity Monitor utility

Clicking the Energy tab in Activity Monitor presents each App’s and each process’ Energy Impact on the system

You can determine if an app is currently using App Nap by looking at the App Nap column next to the name of the app in the Activity Monitor window.

Click Energy near the top of the Activity Monitor window to see how much energy is being consumed by open apps and background processes. It goes without saying that the amount of energy being used affects how much overall energy your Mac is using, and how long you can operate your notebook Mac with no power adapter connected.

Energy Impact – The Energy Impact section shown at the bottom of Activity Monitor’s window represents the total amount of energy used by all apps and other processes over a period of time. To determine how much energy is being used by individual processes, look at the number that appears in the Energy Impact column next to the name of each process. The lower the Energy Impact number, the less power the process is currently using.

The bottom area of the Energy section of the Activity Monitor utility

The bottom area of the Energy section of the Activity Monitor utility displays graphical representations of Energy Impact data and battery usage

Battery Graph – On notebook Macs, there is a Battery graph at the bottom of the Energy section of the Activity Monitor window. This shows the battery's charge level over the past 12 hours. The sections of the graph with a green background indicate times when the Mac was receiving power from a power adapter.

Graphics Switching – Finally, Macs that support automatic graphics switching save power by using integrated graphics and switch to a higher performance graphics chip only when an app needs it. Activity Monitor shows "Graphics Card: Integrated" when using integrated graphics, or "Graphics Card: High Perf." when using high performance graphics. To identify which apps are using high performance graphics, look for processes which list "Yes" in the Requires High Perf GPU column.

In conclusion, as time goes on, we should see our favorite developers embrace the energy saving technologies into their apps. Apple now gives them the tools to make this happen. And, Apple gives us the tools to monitor compliance. By all means, if a few months pass by and our preferred apps are singled out as being energy hogs, then a little nudge or two to the developers via emails or a tweets may provide enough incentive to get with the program.