Battery life is always bad right after installing a new major iOS release. Every time. Give it a couple days, it’ll probably be fine. Most of the time, turning off wifi to preserve battery is more superstition than real.
In fact, turning off Wi-Fi can hurt battery life. LTE requires more power, GPS kicks on more often, and if you have an Apple Watch, data transfer is forced to use Bluetooth which means both devices remain in a high powered state for longer.
> Most of the time, turning off wifi to preserve battery is more superstition than real.
This is not true in my experience. Having the WiFi radio on while network connectivity (including LTE/3G) isn't used hurts the battery runtime. It may be true for Bluetooth Low Energy, but not WiFi. Even when "disconnected" from a network, the WiFi radio now keeps looking for networks soon after the disconnect (I did see a "searching for network" message below the WiFi button in Control Center).
I'm not too keen to hear this news, but there is a tradeoff in that now you can quickly enable low power mode from control center. I still would like a way to entirely disable these connections at times, but in terms of battery there's a bit of give and take.
Don’t try to tell that to the iOS Beta subreddit on reddit. They swear up and down that there is absolutely no battery loss from having your WiFi and Bluetooth enabled even when not connected. To even question this is considered heresy.