>>How likely that would be a coincident?
People say this all the time but literally no one has been able to prove any kind of secretive listening-based advertising.
The best explanation is that either you or someone else in your household has searched for something related and now it's appearing in your ads, or actually more likely, advertisers are incredible at linking cookies to actual users, and it's enough if your friend searched for solar panels and then his interests were associated with you. Like, advertisers can figure out all your friends have solar panels but you don't - so they show you ads for them. It's far easier to do than listening and to your conversations covertly.