Sorry for not being clear, I am comparing the battery life of MBA 13 inch i7 512GB +8GB RAM 2015 model with the MBPr 13 inch i5 512 GB and 8GB RAM 2015 model and it seems that the battery life is always quoted at being longer by several hours on the MBPr compared to the MBA
I wonder does the i7 in MBA use more power than i5 in MBPr while simply web browsing.