Creating simple reflections that doesn't KILL FPS?

So I am trying different ways to create a simple reflection on a window. about the size of a door.

reflection probes kill my FPS (from the 100's to like 15-20fps)
I tried using a water shader with planar reflections and setting it to 0 waves 0 ripples (basically looks like ice).
I've also tried using a plugin that uses a camera system but doesn't work when incorporating cinemachine to my game.

But is there another way for this? using the regular built in pipeline?

 

reflection probes are gonna be pretty fast. Basically just one texture read. Maybe it is because the reflection probes are breaking your batches.

 

I’m am not sure I understanding the reflection probe setting I even reduced the reflection distance from 1000 to 40. And the resolution to 256 and it’s still hogging down the FPS. Mind you this is for a constantly reflecting mirror. Not just on wake. No time slicing

 

So you use realtime reflection probes that refresh every frame? I haven't done any testing with them, but as I understand it, these are extremely expensive, since to build a cubemap reflection probe has to basically render six views (once for each side of the cubemap). And doing so for every reflection probe every frame... yeah...
Using planar reflections with a secondary camera is the way to go I think. I'm not sure what was the problem with incorporating it with cinemachine, but I think it should not be very hard to fix.

 

Yea I use the cubemap
i will keep trying with frozen water lmao

 

Yea that seems to be the case. Thanks again guys.