"Will shade help central air unit? "
Any metal on your AC (heat pump) that's exposed to sunlight is going to be heated up.
It can get hot enough to burn your skin.
The refrigerant in the coil is releasing heat that was
pumped from inside your house.
If the sun is shining on those coils, heating them up, it's going take more work
to cool off the refrigerant & the coils. Using more power.
When it's a cloudy day and not too hot, your AC doesn't have to work so hard.
If you read a few AC installation manuals, most of them will tell you to install the outdoor unit,
where it is not in direct sunlight all day. Being on the shaded side of the house is always better.
My Sanyo is on the east side of my house. No direct sun after lunchtime.
And the early morning sun is blocked by the garage. At high noon in the summer, the little snow roof helps some.
In the wintertime, I want the outdoor unit to be hot!
That's when all that shade is working against me!
But, the warmth from the ground heats up the air a little. Add some solar heat,
and the air going into the Sanyo has enough stored heat to keep us nice and warm..
That's my story, and I'm sticking to it..