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What is the 15-Inch "Late 2008/Unibody" MacBook Pro battery life in "real-world" tests? What is the difference in battery life when using the NVIDIA GeForce 9600M GT and the NVIDIA GeForce 9400M?
Please note that all Macs mentioned in this Q&A have been discontinued. The "Late 2008/Unibody" 15-Inch MacBook Pro models were replaced by the "Mid-2009" 15-Inch MacBook Pro models on June 8, 2009.
Apple reports that the 15-Inch "Unibody" MacBook Pro models provide "5 hours of wireless productivity" with a "Better Battery Life setting" (using the slower NVIDIA GeForce 9400M). The company further defines "wireless productivity" as "wirelessly browsing various websites and editing text in a word processing document with display brightness set to 50%".
By comparison, for the previous 15-Inch MacBook Pro models -- the "Early 2008/Penryn" line -- Apple estimated "5 hours of wireless productivity" performing the same test. It is also worth noting that the "Early 2008/Penryn" MacBook Pro models have a 60 W/Hr Li-Poly battery, but the "Unibody" models have a smaller 50 W/Hr Li-Poly battery, so the formal estimates indicate substantially improved efficiency.
However, regardless of the numbers provided by Apple, it is important to see how the systems perform in impartial "real-world" battery life tests. Additionally, as the "Unibody" models have dual graphics systems, it is important to compare battery life using both the higher powered NVIDIA GeForce 9600M GT and the more efficient NVIDIA GeForce 9400M.
Real-World Battery Life Test Results
Using the 9600M GT graphics card, the 2.53 GHz MacBook Pro lasted 2 hours, 12 minutes, while the 2.4 GHz MacBook Pro lasted 2 hours, 18 minutes. You’ll barely be able to watch an entire movie in that amount of time. . .
Unfortunately, when using the 9400M, the battery life for either MacBook Pro model did not improve significantly. The 2.53 GHz MacBook Pro gained 17 minutes, while the 2.4 GHz MacBook Pro lasted 13 minutes longer. Interestingly, the 9400M times between the MacBook Pro models and the MacBooks are similar.
Comparing the MacBook Pro’s 9400M battery life with the previous MacBook Pro ["Core 2 Duo" 2.4 15" (Early 2008/Penryn], and the older MacBook Pro comes out ahead by 15 percent -- the older MacBook Pro's battery lasted close to 3 hours.
In an in-depth review, the comprehensive ArsTechnica put the "Unibody" MacBook Pro through its paces and covered general use, playing a DVD, and gaming. In the "general usage" test -- which included simultaneously browsing the web over 802.11n, playing music with iTunes, chatting over IRC and iChat, syncing over MobileMe and backing up hourly with Time Machine -- Ars found:
While using the 9600M video card under this scenario, we were able to eke out just under 2.5 hours of battery life. Not outstanding, to be sure, but fairly par for the course for a working laptop. Switching the video card over to the 9400M gave us another 45 minutes of battery life, finally running out of juice after 3.1 hours.
In detailed testing as part of an extensive onslaught of tests that should be read in its entirety, the well-respected AnandTech discovered that the "Unibody" MacBook Pro provided 5.03 hours of use and the previous "Early 2008/Penryn" models provided 5.13 hours of use in wireless web browsing, concluding that "the [Unibody] MacBook Pro battery life remains basically unchanged" using the NVIDIA GeForce 9400M.
For the NVIDIA GeForce 9600M GT, Anand noted that battery life dropped from 3.13 hours to 2.37 hours in "heavy use" and concluded:
Using the dGPU dropped battery life by 24%, which is close enough to Apple's numbers [a 20% drop] to call them relatively honest. I also appreciate that Apple's 5 hour battery life is about what I got with the MacBook Pro in my web browsing test. Honesty is very important in any relationship, even if it's one between a manufacturer and a consumer.
Battery Life Summary
Ultimately, it appears that Apple's battery life numbers for the "Unibody" MacBook Pro models are fairly realistic for day-to-day use making an effort to conserve the battery, but in general, battery life is inferior to the models replaced when using the NVIDIA GeForce 9600M GT and similar when using the NVIDIA GeForce 9400M.
However, as Apple notes as well, battery life may vary depending on "configuration and use" and this is clearly reflected in the variety of real-world tests performed.