Moneyquote: "The temperature of the surrounding air has a much bigger effect on cooling efficiency than direct solar gain, and the volume of air pulled in by an air conditioner is huge."
This article you are referring to is for a heat pump and so are the % of savings.
An AC Condenser sitting in the Sunlight will naturally be a lot hotter in temperature than one sitting in the shade. For example park your car in the sunlight and then park your car in the shade? Where will the surface of your vehicle be hotter/cooler? It has nothing to do with air temperature at this point. It is the heat of the sunlight that is raising the temp of the coils in the condenser just like it would raise the temp of the surface of a vehicle parked in the sun instead of the shade.
A typical small AC will have to dissipate about 5kW of heat through the radiator. If you put it into the sun, it will additionally need to dissipate the energy it gets from sunlight. Assuming that the area exposed to the sun of the radiator is about 0.25 square meters, it will receive at most 250W of energy from the sun (assuming that it is painted black and perfectly absorbs all light and miraculously doesn't emit anything).
This means that you can save at most 5% by putting the radiator in the shade.
(Metal sheets heat up quickly in the sun because they have low heat capacity. They also cool down quickly if you blow on them with a fan. Just because something feels "hot", it doesn't mean that a lot of energy is stored inside)
It's not just the unit itself, but everything the sun shining on nearby heating the air which is getting blown through the coils. The temperature increase effect is also superlinear; the efficiency goes down as the temperature increases so 250W extra heating might cause an extra 120W of loss (that number is made up, but the amount is greater than zero).
https://www.energyvanguard.com/blog/will-shading-your-air-co...
Moneyquote: "The temperature of the surrounding air has a much bigger effect on cooling efficiency than direct solar gain, and the volume of air pulled in by an air conditioner is huge."