Lenovo purports that the battery on both LaVie Z units will last for up to 9 hours. Of course, battery life will depend on how much you require of the system throughout the day, and quoted times have historically been "best case scenario" results. That said, we did feel comfortable that the average user could get 7-9 hours here, but those stressing the system by engaging in gaming or HD video playback will see shorter durations on a charge.
In an attempt to quantitatively measure the battery life in a controlled benchmark environment, we ran two tests to get a sense of how long the system will last under light and heavy use. Our web browsing test is a light-use scenario in which it refreshes a webpage over a Wi-Fi connection until the battery is exhausted. For this test, we set the display to 50% brightness and connected to the web via a wireless network.
The Battery Eater Pro test gives the machine a much heavier workload to simulate the kind of stress you might put on the sytem with multiple resources engaged including CPU, GPU, memory and hard drive.
While performance was great, it comes at a cost. With the screen at 50% brightness, we mustered fewer than six hours in our custom web browsing test -- a full three hours short of Lenovo's own quoted time. Of course, high-end specs with plenty of power will take a toll on battery life. This probably isn't the ideal machine for you if you routinely need 9+ hours between charges, but it does strike a solid balance. For many, even 5.5 hours away from an AC outlet will suffice.