Apple's 2010 MacBook Air (11 & 13 inch) Thoroughly Reviewed

The Battery Life

Light Web Browsing

Here we're simply listing to MP3s in iTunes on repeat while browsing through a series of webpages with no flash on them. Each page forwards on to the next in the series after 20 seconds.

The display is kept at 50% brightness, all screen savers are disabled, but the hard drive is allowed to go to sleep if there's no disk activity. The wireless connection is enabled and connected to a local access point less than 20 feet away. This test represents the longest battery life you can achieve on the platform while doing minimal work. The results here are comparable to what you'd see typing a document in TextEdit or reading documents.

As glorified typewriters, you can’t beat the battery life offered by the MacBook Air. Light web browsing, document creation and music playback have minimal impact on the Air’s battery life. In fact, we actually beat Apple’s battery life claims in our light tests. The 11-inch Air delivers nearly 7 hours on a single charge and the 13-inch managed 11.2 hours. For a writer, you can’t do better than this.

Flash Web Browsing

The test here has three Safari windows open, each browsing a set of web pages with between 1 - 4 animated flash ads per page, at the same time. Each page forwards onto the next after about 20 seconds.

As always, the display is set to 50% brightness, audio at two bars, screensaver disabled and the hard drive is allowed to go to sleep if idle. The wireless connection is enabled and connected to a local access point less than 20 feet away.

If you use the MacBook Air as a full function P...err Mac, the battery life drops steadily. In our Flash web browsing test battery life dropped to 4 - 5 hours depending on which Air you’re looking at. And the difference between the two isn’t all that great. The 13-inch only managed an extra 30 minutes of battery life.

Multitasking Battery Life

Our final battery life test is the worst case scenario. In this test we have three open Safari windows, each browsing a set of web pages with between 1 - 4 flash ads per page, at the same time. We're also playing an XviD video in a window all while downloading files from a server at 500KB/s.

Our heavy multitasking test is the biggest issue. Neither MacBook Air was able to deliver more than 3 hours of battery life on a single charge. The problem here isn’t just battery capacity but also the performance of the CPUs themselves. A major component of long lasting mobile battery life is a concept known as rush to idle.

Let’s say we have two CPUs. The first is an ultra low power CPU that only consumes 10W under load, but 0.5W at idle. The second is a high performance CPU that consumes 40W under load and 1W at idle. If it takes the first CPU 5ms to decode a frame of video at 10W but the second CPU can do it in 1ms, the total energy consumed over 33ms is is 0.064J for the first CPU and only 0.036J for the second CPU.

The longer the first CPU is idle, the more its typical and idle power advantages will come into play (hence the results in the light web browsing test). The more CPU bound the workload however, the more the advantage over the second more high performance CPU will disappear. Our heavy downloading/multitasking test is the most CPU bound of all of our battery life tests and the workload is consistent regardless of how fast you execute it. In other words, a faster CPU won’t be able to do more work, it’ll just be able to rush to idle quicker.

The battery life story boils down to your usage model, even more so than with the MacBook Pro. Light users are going to get wonderful battery life out of the new MacBook Air, particularly the 13-inch model. However, if you are the type of user who does a lot of multitasking or if you’re running particularly CPU intensive apps (e.g. Photoshop, iMovie, etc...) then these two notebooks will hardly last you. I suspect this is the distinction Apple is looking to make. If you’re a regular user, just playing around on Gmail and browsing the web then the MacBook Air is all you’ll need. If you are doing any work with your machine however, you’ll want to look towards the MacBook Pro.