I've been running Avast! on my new laptop lately and surprisingly Avast! is so light-weight... Screenshot:
http://bit.ly/2aQUZp8I love Avast! since it doesn't pop-up some annoying "ads" unlike other free av's like Panda.
Avast! has been my recommended anti-virus since when I was young, now it's a cloud anti-virus; awesome speed in scanning; and, the most important part of an anti-virus, the virus definitions.
Avast! has a free version yet the virus signatures are very good in free anti-virus standards. That's why I love Avast!
I don't mind the ads on the GUI because what's important is your PC being protected.
Keep up the good work Avast!