For solar panels, many people might be interested but also concerned how they look. When another neighbor gets them, people will get used to how they look, realize it’s not so bad, then be more likely to get them.

I don’t think the final conclusion necessarily follows, not with this example. Solar panels are big and obvious on top of the house. It’s not the same thing as other types of values spreading through a community. The house of a healthy person isn’t any different than that of an unhealthy one.

It could be simply that the door to door solar panel salesperson was covering that 1 km area.