Does Avast noticeably affect battery life?
Solution 1:
I tried installing Avast and adding this to crontab:
* * * * * ps -o \%cpu= -p $(pgrep -i com.avast) | awk '{s+=$0}END{print s}' >> ~/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
Solution 2:
In general; yes. Most anti-virus programs do on-demand scanning, meaning they check all files as they are being requested by various programs. This real time scanning requires drive access, processing and some memory, all of which contribute to a slower machine with less battery life.
However, I'd heavily advice against the use of anti-virus programs on Macs. Anti-virus programs for Mac usually don't have any Mac virus signatures that they check for. The main point of these programs is to check for Windows viruses, and prevent accidental infection of coworkers'/family/friends' Windows PCs. Mac anti-virus programs tend to be scams, which although may offer legitimate detection of Windows virus, are simply meant to pray on users and push them into purchasing a paid product.
Apple does a GREAT job at patching up various vulnerabilities, so you should rest assured that your machine is very secure, as you're likely not a high profile enough personality to be worth the effort to hack.