We're about to get a split AC for the living room and kitchen. The apartment looks as follows: enter image description here

The issue is the placement of the units. There are two viable options:

  1. Place it in the kitchen (as shown in yellow).
  2. Place it in the living room (as shown in orange).

Aesthetically, it would be better to place it in the kitchen as the outer unit would sit in the distant corner of the balcony. However, that corner gets a direct sunshine in the afternoon, whereas the other side is already quite in a shadow in the afternoon. (Note that the outer unit should sit on the balcony floor and not be suspended as there's thick thermal insulation which should be touched as little as possible.)

My question is: how much does the direct sunshine decrease the AC efficiency?

  • I would think that the living room location would be better. An air handler in the kitchen may get clogged with grease. On the other hand the filter may collect any grease and the kitchen without a/c may become uncomfortably hot. Do you have a vent hood over the stove which vents to the outside? (Some vents just recirculate through a filter.) Is the insulation you speak of exterior to the load bearing surface? How do you plan to carry away the condensate water from the air handler? – Jim Stewart Feb 16 '18 at 9:53
  • @JimStewart The grease from cooking should not be an issue, the cooker is in the opposite corner and the AC would sit above the dining table. See the updated figure. --- The unit we would get (I know it as we have it elsewhere) allows the condensate to be collected on the balcony, where we would water plants with it. --- I'm not sure what you mean by "Is the insulation you speak of exterior to the load bearing surface", the problem is that it's some 10cm of polystyrene on the outside. It's fine to drill holes through, but it's not so fine to let the heavy exterior unit hang on it. – yo' Feb 16 '18 at 10:04
  • I suppose the balcony is not really large enough for lounging on, so there is no reason not to put the condensing unit on the floor. Maybe it gets it out of sight too, and I could imagine a building management requiring them to be on the floor of the balcony. Is the wall of the balcony solid or a grill work? – Jim Stewart Feb 16 '18 at 10:42
  • @JimStewart It fits there, we've measured it. The wall is reinforced concrete below the insulation, as almost everything here :-) – yo' Feb 16 '18 at 10:43
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    Every A/C unit I've ever seen has been installed in the direct sun. I assume if you ever installed one on the northside, you'd need to arrange some heliostats or something to blast it with solar rays. No idea why, it seems like it would hurt efficiency. – Harper - Reinstate Monica Feb 16 '18 at 17:37

Solar gain in the cooling fins is negligible. Air temperatures in the sun and in the shade are not substantially different if there's any breeze at all, and as soon as the fan starts up the fins reach operating temperature regardless of initial temperature. Ongoing solar gain is minor compared to the overall heat transfer taking place through condensation of the refrigerant.

More important is access to a fresh air supply so recirculation is minimized, and you could always install a sun screen or small pergola if you think otherwise.

More reading


I almost always locate the compressor on the floor / ground. I have in 1 case hung a small unit on a wall because the owner wanted to save $ on the line set. After several months the owner contacted me to put the unit on the floor because the vibration on the wall was anoying. As far as location I will usually locate the unit on the south side because that's where the evaporators are usually located, on mini splits I don't worry about sun/shade loading because in. The winter when the system is being used for heat the sun loading would be helpful and off set summer loading issues.

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    No heating in winter needed really as we've got cheapish central heating. So do I read it right that you don't consider the direct sunshine an issue, please? – yo' Feb 16 '18 at 14:54
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    I do not consider direct sunlight on the unit in most cases the location of the unit for the proximity to the inside units and possible places available to place the pad ( all the units I have installed require a solid foundation). If there is a convient location in your case shaded and you only plan on using AC go with the shaded area it will make a difference but not a large one in my experiances. – Ed Beal Feb 16 '18 at 17:29

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