Battery drain is always difficult to solve. There are many different reasons for it: your specific device model, combination of rom, kernel, gapps, installed apps, usage of gps and wireless connection etc. There's always a chance a custom rom has higher battery consumption due to incompatibilities between this mentioned combination.
First, you should check the steps
@Retrial described in his tutorial to flash the latest rom (eg make sure, you've installed latest bootloader and modem)
Welcome to S4 Unified Guides! This thread now redirects to here. ⬇
forum.xda-developers.com
You can always go back and flash a stock rom with odin.
If you want to know what exactly is the cause for the higher battery drain, you should install a battery monitoring app, e.g. BetterBatteryStats and GSam Battery Monitor.
GSam Battery Monitor provides deep insights into what is using your battery.
play.google.com
I started BetterBatteryStats because I was missing the great battery history that Spare Parts allowed to call on Froyo. It has been a long journey since the first version. BetterBatteryStats provides an insight in following categories: - General...
forum.xda-developers.com
They are not very easy to use, installing requires root or granting special access to system logs with adb commands. But all required steps to install and to read the results are described in detailed descriptions.