I've never had Windows Defender use a noticable amount of CPU. It is, by far, the least intrusive antivirus/anti-malware that I've used (and I've used them all)

I've never had Windows Defender use a noticable amount of CPU. It is, by far, the least intrusive antivirus/anti-malware that I've used (and I've used them all). Unfortunately, I can only provide my anecdotal experience, but it seems to be in stark contrast to your comment.