Default [Q][Battery][Underclock] Battery life

Hi!

Just asking (hope this is in the right place) right now I'm running PA 4.2 beta 4 on My XT912ůstock kernel because JBX have an issue with PA, so, I wanna now, if I underclock my CPU, for example from 1200 to 1000mhz, will I have more battery life? And if it does, the performance changes a lot?

Thanks!

Moto Droid RAZR XT912/PA 4.4.2 beta 4/SS 3.72/Stock Kernel.....Hit thanks if I help greetings from CR
Tapped from my Huawei P6-U06
Latest TWRP
ParanoidAndroid 4.4.4
Stock Kernel
8GB+32GB SDHC