Through the Opera Browser Developer Channel you can try the developer’s version that has a dedicated power saving mode that is engineered to extend your laptop battery life up to 50%. In comparison to some of the other browsers (such as Google Chrome) this can mean several more hours of internet browsing time before you need to recharge your laptop.
Here is how to turn this feature “on”:
It’s easy to use the the new power saving mode. Once the laptop’s power cable is unplugged, the battery icon will appear next to the search and address field in the Opera browser. Click the battery icon to activate the power saving mode and flip on the switch.
You can learn more about this at Opera Blogs