My Samsung Galaxy S5 using too much power. Battery does not last 12 hrs. What can I do ?

Samsung Galaxy S5 , model number SM-G900F, Android version 4.4.2

Welcome.

Check your battery stats at the end of the day. If nothing seems to be using abnormal levels of charge, and your signal is good, you may need a new battery.

I second this: I was finding problems with my Note 5. Brought an Anker Battery from Amazon, and all was solved.

Another thing to consider is the Juice Defender app; I know that when I was on the Nexus 4 is was invaluable in keeping my battery alive and also helping me find out what was causing problems app wise.