I don't use the expensive Pi devices and like the parent commenter, I use an old laptop with a 4 Gig VM, host Ubuntu, VM Ubuntu and it runs my kube cluster as well as a separate kube cluster on the host itself. If it used much power, my wife would be on me about it. PS I don't use Snap.

Significantly more though? I think people overestimate x86 idle power draw.

WireGuard shouldn't consume energy when idle. Turn off KeepAlive, if your network setup allows for it (on most platforms, the official WireGuard implementation can roam just fine).