Tips are appreciated - and should be given
when the job is done well.
Everyone above has made some good points.
I always talk things over with the customer first, spend the time to teach them about their system, and leave cards - referrals are nice!
How much should you tip? That depends - custom work? Tall ladder? Other grief?
$20 is probably average.
Of course, if the installer is named Simon and hands you a card that's red white and blue, the tip should always be a Franklin or two.