I know Anker’s battery packs and chargers will help you to refill the juice however, if you don’t have access to one of those and need to save your phone’s battery for little longer, dark mode is the way to go.
I’m definitely dark mode everything! Whenever I’m in an app that doesn’t support it yet, I find myself doing the smart invert to get it to dark mode that way. 
I love dark mode. So much easier to see.
Once I started using dark mode, I can’t stop using dark mode on every app 
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Battery saving only on OLED displays.
I started using it and found it drained my battery quicker 
Turns out that my dark mode addiction is actually a good thing!
I have an XR with an LCD screen so no. It doesn’t save battery