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My laptop is getting much shorter battery life than advertised, and obviously that's going to be due to some code running that's draining it faster than is optimal.

How can I (using Mac OSX 10.6) determine which applications are hitting my batteries hardest?

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All laptops get shorter battery life than advertised. It's called "Advertising for the absolute best case scenario in order to make your product look better". See also: lifetime of appliances, gas mileage of your car, etc –  Shinrai May 18 '11 at 16:56
    
How much shorter is 'much shorter'? If you're getting 4 or 5 hours, that is probably average, if you're getting less than 2 there's probably an issue. Also, what Macbook do you have? They all have different lengths of advertised battery life. –  Connor W May 18 '11 at 17:05
    
Reviews of the MBA have indicated that routine usage actually provides better than advertised battery life. ex: osxdaily.com/2010/10/30/macbook-air-2010-battery-life I'm not saying I'm expecting this, and it's also not relevant to my question; I'm not interested in "is this okay?" I'm interested in "what's the cause of this?" –  Chris R May 18 '11 at 17:06
    
@Connor Macbook Air, latest model. Projected battery life is ~ 3.5h, instead of 7-11 –  Chris R May 18 '11 at 17:07
    
In my case it was three Java applets still running after the windows that had spawned them had been closed. 100% CPU on three separate cores (out of four). Fan was cranking hard, and as soon as I killed them CPU usage dropped to <5% and fan shut down. As for why I even have Java installed, long story involved mandatory work webapp that uses it heavily. :( –  Adam Wuerl May 12 '13 at 20:10

4 Answers 4

I second @Connor W's suggestion of using Activity Monitor (or "top" from the terminal) to see what's using the most CPU. Unfortunately, that might not show what's using the most GPU, and the GPU has plenty of potential to burn power.

Here are some additional battery-saving tips:

Make sure you have a Flash blocker installed. I like ClickToFlash. It's Safari-only, but there are similar tools for other browsers as well.

Flash is the most notorious CPU/battery hog, and is often running just for ads. I seem to recall a study that estimated that on a Mac with default out-of-the-box settings, under typical web usage, over 10% of your battery life goes to Flash ads alone.

Most Flash blockers also allow you to load native H.264 video from popular video-sharing websites like YouTube and Vimeo. Mac OS X's native video-playback code is much more efficient than playing via Flash.

Avoid using Flash for long-running services like Internet audio streaming (Pandora, Grooveshark, playing podcasts directly from a web page, etc.). Download a native Mac OS X client, or opt for their "HTML5" version, or opt for a standard format audio stream that a native Mac app such as iTunes can play.

Don't keep your backlight on max if you don't need it. Don't power things via USB if you're not on the power adaptor (don't leave iPhones and iPads tethered, eject your flash drives and 3G cards). Turn off Bluetooth and AirPort when not in use.

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Airport and bluetooth are great suggestions. Radio transmission is a power hog. –  horatio May 18 '11 at 20:40

The first thing I would check is the Activity Monitor for applications that are running with a high CPU usage.

Activity Monitor can be found under /Applications/Utilities/Activity Monitor.app

In the app, click the CPU column to filter the processes by CPU usage, and then watch it for a while. If you see one application that regularly uses the CPU a lot (>60-80%), that will be reducing battery life. Try closing it and see if the battery life improves.

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Make sure you don't have "kies wifi agent" running in the background.
Reduced my battery life from ~6h to <2h. Deleted the program and things went back to normal.)

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In Linux we use powertop. Although I've never used it many people recommend it to investigate power leaks. It even records the many cpu sleep states.

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