I treat them just like spam calls. If i didn't ask you to come, I'm not even opening the door.
Door to door salespeople prey on the "decency" of homeowners to always answer when someone knocks. Stop opening and they'll stop coming.
All of the solar companies basically charge you $10-15K to act as the general contractor as they sub out the roofing and electrical work. Act as your own GC. You can source your own solar equipment and get a roofer and electrician and you will be able to get as many panels as you want and pay significantly less.