I have an iPhone 6s & had the same problem. I’ve read numerous articles on how to save battery life and have implemented all of them. I downloaded 14.2 & it seemed okay. Then one day, after a 100% recharge, I set it down & didn’t use it all day. When I picked it up, it was at 1%!!! I looked at battery life & Siri had used 100%!!! I had it set up to access Siri only when you pressed the home button. I undid anything related to Siri. I did some of the tips suggested on this forum, except factory reset. Finally, I turned her completely off. My phone is back to normal. I miss her but I had to chose between her & battery life. I understand that 14.3 has been released & unless it has addressed some of these problems, I will not take the update. However, I will keep this phone until it completely dies, any apps that quit working will be deleted. (& in the meantime I should start saving my money for a new iPhone.....unless an other & better brand comes along).