iOS 14.3 BATTERY DRAIN ON STAND BY

Hey there

That's certainly not the experience we would want for anyone after updating their operating system. We're happy to provide guidance.

From the screenshot you provided, Home & Lock Screen is using some of the battery life. To help with this, tap Settings > Notifications. You can change your app notifications to use less battery life by turning off "Show on Lock Screen". This causes the iPhone screen to turn on every time you receive a notification. 

You can also learn more about what is using the battery with the guidance here: About the battery usage on your iPhone, iPad, and iPod touch

Tap Settings > General > Background App Refresh. Review the apps that are using this. You can turn this off for all of your apps and help with the battery as well. 

We have some additional steps you can take using the guidance here: Maximizing Battery Life and Lifespan

Take care!

These canned "you're doing it wrong" responses are not helpful. There are hundreds of posts by people losing substantial battery on standby. My 12 Mini lost 62% last night in 6 hours! I have owned iPhones for over 13 years and can say with certainty this is not normal iPhone behavior.

I have an update here. Last night I changed my Mobile Data Option from 4G to 3G, turned on Low Data Mode, deleted the default Mail App of iOS and restarted my phone. These 3 changes were done after all the Battery Saving Tips on YouTube failed for me. To my surprise, I did not see even 1% battery drain overnight (7 hours of standby time) when the battery was charged >= 90% but lost only 4% overnight battery drain when the battery was charged somewhere around 75%.

Many of us are experiencing this; you might be interested in this thread: https://discussions.apple.com/thread/252151864