I can confirm this behaviour in 1.8.1 with a nvidia Geforce RTX 2070
It was not that way in earlier versions:
Doing nothing in Chitubox makes the GPU run damn hot when it's open. I once forgot to close it and i almost burned myself when touching the keyboard of my notebook on returning. That can cause serious hardware problems if unchecked.
It does go down to normal when minimized for some reason, but being open (even in the background) = almost unusable after a while
Any chance of posting a beta with the gpu fix. Im running a 8 core intel i7 with a RTX 2060 and this program is running really slowly on my machine and using about 80% of the GPU while its doing nothing.