I'm sure it depends on the country, but in my country (Spain) you can literally go and buy solar panels in the local hardware store and install them without per

I'm sure it depends on the country, but in my country (Spain) you can literally go and buy solar panels in the local hardware store and install them without permits, even for renters given you don't destroy anything. And besides that, most owners (as a renter) are OK with you installing solar panels. Never owned a place, had solar panels installed in the last three places I lived in, the first two were apartments, currently renting a house. None of the owners had problems with us installing solar panels.