On an average battery usually performs lower than the officially quoted value, for example MacBook must give 4.5 hours of time. This is dependent on many factors, mainly on how you are using your notebook. There are few things which can help you save your Macbook’s battery life.

Make Best use of the Battery life settings.
You can go to your battery settings, click on Energy Saver Preference. Choose Battery and set the optimization for Better Battery Life. This would automatically put the display to sleep when it is inactive for more than a minute and this may reduce your processor performance. Your MacBook will not run quite as fast, but get to save more battery power by doing this.

Power down your hard disks
By Powering down your hard disks, while you don’t need them also helps in saving energy To do this you would need to go to Energy Saver Preferences and enable the Put “Hard Disks to Sleep When Able”, option.

Lower down your screen brightness
By Lowering down your screen brightness you can save your battery’s life immensely. To do this go to the Displays Preferences pane on your Macbook and then adjust the screen brightness down a bit. Also remember to disable Auto Adjust.

Turn off Side Applications
By turning off Applications that you don’t require while working on your macbook, also helps. If you do not need Airport, Bluetooth when you are not using them, please turn them off and you will notice that battery is giving longer life to you.

Lessen the Widget Load
By closing Dashboard you can save battery life, with no widgets turned on, it saves some power.

Batteries die out eventually and with time their efficiency also goes low. To increase life of your battery, follow small tips from above and also for sake of a regular monthly maintenance. Just once in a month you must run your MacBook on battery until it puts itself to sleep, indicating the battery is empty. Then plug it in and recharge it completely.

The battery life on Macbook is greater than other laptops I have used. OS X has plenty of different settings while your are using battery power, the energy saving mode clocks down CPU, you also have normal and performance mode. Apple has officially quoted 6 hours of battery life if you are using it without Wi-Fi enabled and on the energy saving mode, with lowered brightness.