There is an open issue @TrystanLea.

to fix, include this in /opt/openenergymonitor/EmonScripts/defaults/etc/logrotate.d/00_defaults although this will block further update to the emonscripts folder by git.

maxsize 500k

/var/log/logrotate/*.log {
        rotate 7
        daily
        compress
        copytruncate
        size 100k
        nocreate
        missingok
        notifempty
        delaycompress
}

[edit] I have now done a PR to include this fix Fix var log filling up with logrotate log files by borpin · Pull Request #85 · openenergymonitor/EmonScripts · GitHub