I use eset smart security 8 (8.0.319.1) on 2 pc's.
1. win7 pro 64 4GB RAM
2. win10 home 64 8GB RAM
on both pc's the system is close to unusable when scheduled on-demand scans run (run them once a week, scans all local drives)
reaction time for entering values into cells of excel e.g. sometimes 10sec or more (no formulas to be calculated, just values!)
starting other programs like firefox takes up to 1-2 minutes
I am about to deinstall it, never had another antivirus which used system resources as heavily as eset does.