Wifi & Ethernet Together

Wi-Fi and Wired network load preference

Assuming that when you say wifi you mean you are connecting to your LAN using a wifi connection to your router and when you say Ethernet your Ethernet cable is connected to the same router. If so then if wifi is at the top of the list then your computer will always default to using wifi to connect to your LAN. If you lose the wifi connection the Ethernet connection will be used. Is this what you are asking? If not, rephrase your question.

Your Mac will send traffic to the Internet using the TopMost, Working Interface shown in the Networks panel.

It does NOT do real-time load balancing across multiple interfaces, regardless of how many and what type might be available.

So try to put the "best" connection at the top of the list, as JimmyCMPIT suggests in his User tip. If working, that is the one that will be used.

Thank you Grant for pointing out use of the word "balance" in the title of my post was not the case, it's not balancing anything, it's preferring one over the other. I've changed the title for clarity.

I have servers accessible only though my wired LAN which is an entirely different network as my primary network (wi-fi). When I'm on the web which is 95% of my day the network is using wi-fi so all internet traffic stays on wi-fi, but it knows to switch to wired when the Wi-Fi network can not find the path to the server.

The wi-fi in my building is insane fast, or I would just stay on my wired which was has limited bandwidth.

If Wi-Fi is on top, it will only switch if Wi-Fi becomes non-working.