Google has promised that Android M will be much more power efficient than its predecessors, and its preview firmware running on a Nexus 5 confirms that to be the case. In fact, during testing, standby time on the near-two-year-old handset more than doubled.

German website ComputerBase installed the Android M developer preview on the Nexus 5 and monitored its standby times — then compared them to those of Android 5.1.1 Lollipop. The difference is remarkable; M delivers around 2.7 times more standby life.

That’s around 533 hours, or just over 22 days. In comparison, a Nexus 5 running Android 5.1.1 lasted just 200 hours, or just over 8 days.

Over an 8-hour period, Android M consumed just 1.5% battery life on the Nexus 5. After 24 hours, it consumed 4.5%, and after 48 hours, it consumed 9%. Android 5.1.1, on the other hand, consumed 4%, 12%, and 24% respectively.

If you don’t use your smartphone excessively, then, it’s going to last a whole lot longer in between charges once it’s running Android M. That’s mostly thanks to a new feature called Doze, which puts your device into a deeper sleep when it isn’t being used.

When Doze springs into action, network access is disabled, except to apps that have “high priority” notifications from Google Cloud Messaging. Wake locks from any apps are also ignored, Wi-Fi scanning is not performed, and any syncing or updated tasks for apps are not performed.

All of these things are happening on your Android device right now when you’re not using it, causing its battery to drain. But with Android M, that’s going to stop. This comparison gives us a good idea of exactly how much of an improvement Doze will bring.

We should note, however, that this is still a developer preview we’re talking about. If anything, these standby times should only get better as Google makes improvements and optimizations to Android M and Doze ahead of a public release this fall, but it could swing either way at this point.

No matter how much the standby times fluctuate, however, you can be sure that Android M will bring significant battery life improvements to almost any Android device — especially those that run pure Android firmware without third-party optimizations.