How to Use the Activity Monitor Energy Tab in OS X Mavericks

Apple made battery life and energy efficiency a key component of the OS X Mavericks upgrade, and the company provided a number of tools that users and troubleshooters can utilize to monitor energy usage. But included in these tools are a lot of new terminology and concepts that may be unfamiliar to even longtime Mac users. Here’s an overview of the new Energy tab in Activity Monitor, and how you can use it to help maximize your Mac’s battery life.
To launch Activity Monitor, either search for it with Spotlight or navigate to /Applications/Utilities and find Activity Monitor.app. Click on the Energy tab to view important information about your Mac’s energy usage. We’ll examine each portion of this window separately.

App Name: This lists each running application. Apps with related processes will have a disclosure triangle next to them; click it to reveal the individual processes. Apps that are no longer running but have recently used a measurable amount of energy will be displayed grayed out.
Energy Impact: Apple has been a bit cagey when it comes to defining exactly what this measurement is, but company engineers described it to WWDC attendees as a “number that is a relative measure of the energy impact of an app or process,” taking into account factors such as overall CPU utilization, idle energy draw, and interrupts or timers that cause the CPU to wake up. It can go from as low as zero to an indefinite high (the highest we’ve seen it is about 780 while running the Geekbench stress test). The lower the number, the less energy impact an app or process has on your Mac.
Average Energy Impact: This is the average of the above-mentioned Energy Impact value over the past 8 hours (or since the last boot if less than 8 hours). This is valuable because it helps identify energy hogs that may have run in the past but which are currently inactive. It also helps you identify apps that may use relatively little energy, but which are constantly running.
App Nap: This tells you if Apple’s new App Nap technology, which automatically cuts power to applications when they’re in the background, is currently active for a particular application.
Requires High Performance GPU: For Macs that have both integrated and discrete GPUs, such as the MacBook Pro with its Intel HD or Iris Graphics and NVIDIA GPU, this column lets you know if a particular app requires the discrete GPU to function. Discrete GPUs require significantly more energy than their integrated counterparts, but some advanced or graphics-heavy apps can’t run without them. This column will help you identify which apps are causing the discrete GPU to kick-in, and let you decide if the app’s capabilities are worth the hit to your Mac’s battery life.
On the bottom of the Energy tab window are three additional boxes with more information related to your Mac’s battery and power status.

Energy Impact: Using the same measurements as the application-specific Energy Impact calculations, mentioned above, this graph monitors the overall system energy impact of all apps combined over time.
Graphics Card: Based on the discussion of discrete and integrated GPUs, above, this tells you which type of GPU is currently in use on your Mac.
Time Until Full / Time Remaining: Depending on whether your portable Mac’s battery is plugged in and charging or unplugged and discharging, this will tell you how long until the battery is completely charged or how much battery life remains, respectively.
Time on AC / Time on Battery: Similar to the previous description, this reports how long the computer has been plugged in or how long it has been running on the battery. This is helpful for keeping track of your battery usage, as battery life best practices caution against leaving your Mac plugged in for too long.
Battery (Last 12 Hours): This graph shows the charge level of your battery for the last 12 hours. The blue line represents the charge level of your battery (the top of the graph equals 100 percent charge, the bottom corresponds to 0 percent charge) while the green overlays show periods when the Mac was plugged in.
It’s important to note that many of these areas are dependent upon your Mac’s hardware configuration. If you don’t have multiple graphics cards, for example, you won’t see anything related “High Performance GPU” or Graphics Card Type. Similarly, if you’re using a desktop Mac, you won’t see information related to battery charging times and usage.
Based both on public marketing and on statements made to app developers, Apple has made energy efficiency a major goal for the future of OS X. While many of the concepts introduced in Mavericks may take some time to get used to, third party app developers are already working hard to take full advantage of the new OS X APIs and technologies to make their apps as energy efficient as possible. Until we reach the point where most apps are fully optimized, however, users can take matters into their own hands by monitoring app energy usage via the Activity Monitor.