How energy efficient are your plex servers?

I built a plex server using a microATX motherboard with 2 case fans. I’m planning on adding an intel arc a380 gpu and since the server stays on 24/7 will it be using a lot of electric? I believe my power supply is 550 watts. I use open media vault but my motherboard isn’t anything crazy so when I go into the bios I don’t have many options to set the RPM of the fans.