I'm surprised residential PV even interacts with radar -- or is that the other signal intelligence part?

Big flat conductive panels make good reflectors.

Wonder if it can be leveraged as for passive radar. Synthetic aperture also comes to mind.

I’m clueless in this field tho.

That makes sense but my first thoughts were that panels wouldn't be oriented so that the majority of that flat surface was perpendicular to the radar but instead much closer to parallel, and that aviation radar would be higher up than a house roof to avoid ground clutter.

It probably has more to do with the fact that solar that far north is a non-starter. Any PV installed there will actually make AGW and carbon emissions worse, not better. Basically, the amount of carbon emitted due to manufacturing is greater than the carbon savings over the lifetime of the panel in those locations.

Even it that was true, why would the military concern itself with that, and why only for the coasts?

Solar is anti-cyclical with wind both daily and seasonally and an amazing resource during ~8 months of the year in Sweden.

I suggest you stop spreading misinformation.

Since it’s all classified o honestly don’t have a clue. But passive radar is also a thing and something that the Swedish defense industry is fairly good at https://en.wikipedia.org/wiki/Passive_radar.

The best part is that Danish, German and Polish parks are planned mere kilometers away from the denied Swedish ones.

The military will need to figure out how deal with off-shore wind no matter what.

I did the same thing in Sim City: put my coal plants in the corner of town