The new version of Android was put to the test by ArsTechnica and it was found that a Nexus 5 running Android L had a 36% longer battery life than one running Android 4.4 KitKat. In order to test the devices, the screens were kept on, they were connected to Wi-Fi and a webpage was refreshed every 15 seconds. This test was conducted without the “battery saver” feature being switched on, so no additional sacrifices will need to be made when you’re trying to extend battery life.
At launch, Android L will include a stat tracker called "Battery Historian," which gives a breakdown of which apps are draining the most power. Meanwhile, the new JobScheduler API will enable Android batch unimportant app requests together for greater efficiency.
Android L will arrive later this year, so who knows, we may see even greater improvements to battery life.