On the SW elevation of my business, I have the three AC units (heaters are inside- split units).
I have always heard that shaded units cool more efficiently because of the greater temp differential between the coolant and the fins when shaded vs. full sun.

This makes sense to me.

However, not being a heat pump guy, I asked a question to a horticulturist:
"Should I plant something evergreen or deciduous to shade the units for maximum summer/winter efficiency?"
His reply: "Probably something deciduous. You'll get shaded units in the summer and warmed units in the winter."
I asked the same question to my contractor, mistakenly looking for consensus opinion. His reply:
"I can't see how the !@#$ that's going to do a *&^%$#@ thing for you. Just my opinion."

Anybody got 2 cents for this one?
-Hobbit

My buddy, who used to do HVAC residentially, told me that he felt it was useless too when I asked about doing something similar at my house.  However, I think you should try it.