Is it normal for 10-20% cpu to be used when idle and watching activity monitor?

Is it normal for 10-20% cpu to be used when idle and watching activity monitor?

I have a macbook 6,1, 4gb of ram, and my os seems to be spinning the rainbow quite often and laggy. I watch my activity monitor and it never drops below 90% cpu available. Is this normal? if not what can I do to clean up my os. Does anyone have any resources or help? Thanks