Low Battery Performance - Activity Monitor Shows Faults in CPU statistics
In the context of the statistics shown here, the 'faults' represent 'page faults', which are actually benign and refer to an attempt to read something that was not present in memory. This is taken care of in the virtual memory system by 'paging' the requested memory into the memory map of the process. But the OS keeps track of how many of these there were. If the number is very high, it can mean that you don't have enough RAM, or that you have a large number of processes trying to use more RAM than is currently to hand.

Assertions represent something unexpected by the program, and would be indicative of some kind of problem. I would be surprised to see any of those in 'live' commercial software, though.

Things that can drain battery more than expected include:


The Flash plugin. This is a memory hog and should die already.
Google's Chrome browser. It has been shown that using Safari instead of Chrome can add up to an hour of usable battery life. (This is a known issue)