The power consumption results are happening when a late-2010 Apple MacBook Pro with Intel Core i5 520M "Arrandale" CPU was running OS X 10.8 Mountain Lion and then the latest development snapshot of Ubuntu 12.10. (This is the same MBP that was used in the benchmarking earlier today, where the full system details are mentioned.)
In most Phoronix power testing, the Phoronix Test Suite measures the AC power consumption via a WattsUp USB-based power meter that is backed by an open-source Linux utility that works well and the Phoronix Test Suite is able to automatically interface with the program. Unfortunately since the OS X support for the WattsUp power meter isn't on the same level, that ruled out using that device for today's cross-OS power measurements.
When running on battery power, the Phoronix Test Suite can also monitor the exposed ACPI battery information from the OS. However, with not knowing how Apple might be handling their ACPI battery information or if either OS is more or less correct than the other, that couldn't be used either for this testing.
As a result, for comparing the power consumption of OS X and Ubuntu Linux, a trusted SeaSonic AC power meter was measuring the power of the 2010 Apple MacBook Pro at the power outlet. With just running some simple idle and load tests, this ended up working out fine.
the actual C-Ray results were close, so Linux was simply burning through excessive power but not delivering any greater performance-per-Watt.] Under this heavy CPU load, Ubuntu also ended up running the CPU fan at a higher rate than when OS X was running the same test profile. This is what the Linux hardware experience is like on a two-year-old Apple laptop, not even the latest Retina MacBook Pro where Linux is a complete mess.
Two years ago I began using Ubuntu Linux virtualized on OS X when noticing that initially the Linux power consumption was significantly higher than using Apple's operating system. While I've since moved onto using the Retina MacBook Pro as my main production system -- again with Ubuntu virtualized atop OS X using VMware Fusion since Linux is a wreck on the hardware at this point and Linux also has Thunderbolt display problems -- after performing these new clean tests I was rather surprised to see Linux continuing to do so sloppy when it comes to power efficiency.
Ubuntu 12.10 is burning through twice as much power when comparing the stock operating systems when idling and over 20% more power under load against OS X 10.8 Mountain Lion. Linux users can immediately blast Apple with negative comments that they're an unfriendly vendor, they're special since they control both the hardware and software, or that Linux users shouldn't buy Apple hardware, but there's plenty of Apple hardware out in the world that's popular with consumers and this is the experience they see if trying Linux.
It will be interesting to revisit these numbers in another year or even six months time... I'll also try the tests on some other Mac (Mini) hardware around here.