Were you using the userspace implementation or kernel-mode? Kernel mode is supposed to increase performance and reduce battery draw.

Perhaps a kernel is available for your device, or you can look at building and contributing one if not!

What device do you have?

A lot of people who erroneously turn on PersistentKeepalive on their phones wind up with battery drain for clear reasons. Mobile phone users very much should not be using PersistentKeepalive.

Same with iOS. The battery drain was significant enough to make my phone hot even when the screen was off.

The app has a logging facility.

I'm not affiliated with the WireGuard project, but I would appreciate it if you could encounter the issue again, and then submit an account of your experience and the logs from your device.

I have not experienced this on my (older) iPhone, and my Wireguard VPN is always on (to Mullvad).