Thanks for your answers.
Since it’s really just in the background, I only want to place static meshes without any Blueprints to save as much performance as possible. I was thinking something like a noise material that is based on world position and increasing the noise size so much that is always covers at least the size of one full window, but no matter how I tweak it, there are always spots that cover half of a window or several window bits that makes it look like random spots instead of lit up windows.
I’ll probably end up adding another material for light windows on the static meshes and in the 3d program I will manually select a few windows and give it this bright material so in the game you could probably tell the buildings are clones, but as long as I place them far apart from each other it shouldn’t be too obvious.
Still open for other suggestions if someone knows a better solution.