Does Avast noticeably affect battery life? I am thinking about installing the free Avast anti-virus software on my MacBook Air (2012).  Once Avast has completed its first scan of all of the files, does its continued operation noticeably affect battery life?

Is the answer to this question known for alternative anti-virus programs?
I tried installing Avast and adding this to crontab:

* * * * * ps -o \%cpu= -p $(pgrep -i com.avast) | awk '{s+=$0}END{print s}' &gt;&gt; ~/Notes/avast.txt

The average CPU use (for one core) after about a day was about 1.5%, but I'll keep it running for a few more days or weeks.

iStat Menus displays CPU power consumption in Sensors > CPU Package Total. Approximate CPU use and power consumption on my iMac:


5%: 5W
100%: 13W
400%: 25W


So 1 percentage point increase in CPU use (for one core) from being near-idle might correspond to 1-2% increase in CPU power consumption. The ratio might be higher for laptops though. And the percentage change in total power consumption depends on the power consumption of displays and other components.

Idle power consumptions with display off or at maximum brightness:


11-inch MacBook Air: 4.7W, 9.0W
15-inch MacBook Pro with Retina Display: 5.3W, 17.6W
21.5-inch iMac: 14.1W, 41.8W