From a post in the electric bill reduction thread:
Oh boy. Just like in my solar panel sojourn, I have a lot to learn. I've never given a thought to A/C before, not much call for it in Fairbanks, Alaska where I lived for the past 50+ years. So far my research into A/C is like when I tried to learn Unix: everything I learn serves only to expand the horizons of my ignorance.

Off the top of my head I can think of seven general areas of ignorance that I need to address.

1) What general style of A/C is appropriate? There are (a) portable units, (b) window style units, (c) split systems, (d) central A/C, and probably a few others I am not aware of. I am leaning towards (c), the split system, something along the lines of LMU240HE , not necessarily that exact model but of that type.

2) I am not sure how to size the unit. I know there are rules of thumb, X BTU capacity for Y room area, but there are a lot of other factors involved. Here is what I am trying to cool: about 800 square feet, with floor to ceiling glass in three of the four walls. The building itself is completely un-shaded until about 7pm when the sun finally goes behind a big jacaranda tree. The North wall is solid brick and never sees direct sun. The East and West walls have gauzy white translucent curtains. The South wall faces the sun during the day, has no covering, but my awnings do not allow any direct sun to reach the inside of the house; during the day it is not possible to actually see the sun. There will be two A/C outlets (heat pumps), one in the bedroom, the other in the kitchen/living room. The two rooms are of comparable size. There will rarely be more than two people in the house. For 10 months of the year there is no need for A/C, but April and May can be uncomfortable, with outside temperatures in the high 80's, low 90's. Apparently some of these split systems also operate in heating mode. [How does that work?] That might be useful for about 10-15 days out of the year, but not essential. So, given that information, how big a unit would be appropriate? It is my understanding that an over-sized unit working easily will use less electricity than an undersized unit working too hard. Better to err by too much than by too little.

3) Juggling the variables of efficiency, up-front cost, long-term operating expense, and quality can be mind-boggling. Apparently the magic number is the SEER (Seasonal Energy Efficiency Rating) and the US Department of Energy has mandated a minimum rating of 13 for new units sold in the US. Many of units in the 12K--24K BTU range (including the one linked above) seem to be at this minimum rating. Is it cost effective to pursue higher ratings, considering up front costs, operating costs, and longevity?

4) How can I get a handle on my actual electricity usage costs? Yes, dividing the rated BTUs of the unit by the SEER rating will give me nominal operating wattage, but how do I factor in the time variable? For example, my refrigerator uses 50 kWh per month. It is "on" 24 hours a day, so theoretically it is using about 68 watts. But of course the compressor only runs about a quarter of the time, so it really uses about 250 watts, the rest of the time it uses nothing. So if I have an 18,000 BTU, SEER-rated "13", air conditioner, how much of the time is it actually using its 1385 watts? [BTU/SEER] Does it cycle on and off like my refrigerator? If it is on 8 hours a day will I be using 11 kWh a day, or some lesser number? How do I figure this?

5) How do I go about choosing a specific make and model? I see brands like Amvent, Sea Breeze, Klimaire, Turbo Air, Pridiom, Federer, Mr Slim, Global Industrial, Friedrich, Solius, Frigidaire, Napoleon, etc, and that's just for the heat pumps. There's another list of manufacturers for the compressors. Here in Mexico, it's likely to be Manuel's Tacos and Air Conditioners. All I can do, I guess, is rely on recommendations from people I trust. (Hint, hint.) Does anyone here have specific recommendations based on the above information?

6) Power requirements. I will have 220V power available on the roof where the compressor will be installed, I will only have 110V inside the house. Does the inside unit also run on 220V?

7) Installation. From what I have read, this is NOT a DIY process. Special tools are required (vacuum pump, pressure gauge, torque wrench) and fanatical devotion to cleanliness to avoid contaminating the refrigerant. How do I find a competent installer?

Sigh... maybe it would be easier for me just to move back to Alaska.

tanstaafl.