Whether you tip a window washer is up to you, but you can certainly give them a tip if they do a good job. This is a particularly nice gesture for workers who clean your windows under harsh conditions (e.g. hot weather). A tip between $5 and $20 is appreciated. If it’s a crew, you can throw in $5 or more per person, or just go with $20 if it’s a single person. Qualities of a job well done include timeliness, professionalism and friendliness.