people complain they can't install them in their rented flats and all the spoils go to the people who have their own roofs to put them on
For what it is worth, Germany has pioneered what's referred to "balcony solar": a modest set of solar panels, plus an inverter with good safety architecture, which plugs directly into a wall outlet and backfeeds the premises. These get their name from the notion that you can drape the panels over a balcony rail, plug in, and start making power. The systems are modest: a few kW max, but that can make a dent in the energy budget of most flats. Some systems can also pair with modest-sized batteries (oversized power-banks). These systems gives renters with access to sunshine the ability to make some of their own power. They are available in the US now, too, although most states' regulations don't specifically allow them yet. Plus, owing to the differences in Europe vs US home wiring, you may need to be careful about what you plug into.