OpenVPN overhead, 10-15% bandwidth loss normal?

[Sampson]

Hi,

I've recently setup opnsense for the first time on a PC (i7-3770K CPU @ 3.50GHz, 16 GB RAM) which I expected to be overkill for a home router but I already had the hardware available. After setting up an OpenVPN client connection to my VPN provider (ExpressVPN) to route all LAN traffic through the VPN, I was a bit surprised to see bandwidth overhead of approximately 10-15% in both the downstream and upstream. While monitoring a speed test under Reporting->Traffic I can see on the graph that WAN is at the expected bitrate provided by my ISP while the VPN as I said is 10-15% lower. Is this expected? Hoping to get an opinion from more experienced and knowledgeable users. Thanks!