Where solar panels are installed for free (2,3,5)
I believe the answer is:
on the house
'free' is the definition.
(something on the house is given free of charge)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for on the house that I've seen before include "Roof tiles so" , "Where satellite dish may be" , "At the publican's expense" , "No charge" , "With the management's compliments" .)