hows the battery life on Macbook Air 2014 model with recent Ubuntu Release (14+)

I am planning to buy macbook Air 2014 model but i prefer to use Ubuntu for my use. dual booting with ubuntu is not good choice for me when my budget is hardly 128GB model . I am considering macbook air only for its Lightweight and Battery backup . Track pad is not big issue for me as it seems for many users (OS-X users). I am not able to find any solid statement about Battery life with MacBook Air mid 2014 model with recent Ubuntu release say 14+ .