Even though to the uninitiated it sounds like a no-brainer to cover windows with solar panels, it turns out that what makes a solar panel effective is that it c

Even though to the uninitiated it sounds like a no-brainer to cover windows with solar panels, it turns out that what makes a solar panel effective is that it converts the light to electricity and only lets through what it can't convert (which, sadly, tends to be what you can't see). Windows are useful because they let light through. Solar panels are useful because they don't. If you ended up with some sort of hybrid that let 50% of the visible through and absorbed 50% of the balance, it would not be a very good window (too dim or obstructed), and it would cost at least double what a comparable solar panel would cost (per watt). You'd also take some hits to aesthetics and efficiency (humans want reflective coatings on smooth window glass, solar cells want antireflective coatings on textured low-iron glass). Wiring up the windows would likewise add to the installation cost. Solar panels produce their rated power facing somewhere between up and south (in the northern hemisphere), and building windows almost never face in that direction, making for an ever bigger hit to performance. Installing panels on buildings can be a good idea, but not where the windows go. Rooftops and south-facing walls are about it.