How to log system activity the whole day
The average energy impact column in Activity Monitor shows the average energy (or CPU) use for the last 8 hours:



If you have downloaded Xcode, you might use the Activity Monitor template in Instruments:



With top, you can use -a for accumulative display. -o cpu orders processes by CPU use:

top -a -o cpu


To track the average CPU use of processes, run EDITOR=nano crontab -e and add a line like this:

* * * * * ps -eco '\%cpu= comm='|sed $'s/^ *//;s/ /\t/'&gt;&gt;~/Documents/cpu


Then run awk -F$'\t' '{a[$2]+=$1}END{for(i in a)print a[i],i}' ~/Documents/cpu|sort -rn later.