Why in India AC tonnage requirement is 3 times that of a USA desert?

While looking to buy a new AC I searched for many online tonnage calculators.

Indian salesmen:
With ceiling at 9-10 feet, if you carpet area is 100sqft-->1 ton, 150sqft-->1.5 ton, 200 sqft-->2 ton.
To be on safer side by the higher one.

Indian tonnage calculator:
It mainly depends on how much Btu/Hr your machine can cool.
On an average 1 ton=12000 Btu/Hr
But you need

I go to Wikihow.com
Cooling Capacity Chart - wikiHo
and they have a chart that shows 450-550 square feet of area can be cooled by 12000Btu/Hr

I go to about.com
Air Conditioner Sizin
and it says
" simply multiply the length times the width of the room or area to be cooled. Then, as a practical number, multiply that total times 25 BTU. This allows ample cooling, whether it is a rainy, moist day or a hot, sunny, humid day. Let’s say the room is 12 feet wide by 15 feet long. That means 12x15=180 square feet. Take the 180 sq. ft. times 25 BTU per square foot and you get the minimum BTU air conditioner you should buy. That means 180x25=4500 BTU cooling capacity is needed."

I go to Properly Sized Room AC : ENERGY STA
again the same thing

I go to a commercial website that makes Manual J software calculation for air conditioning requirement. There is a chart that shows cooling requirement according to area
What Size Central Air Conditioner Do I Need? A Short Guid
and another website
HVAC Sizing | Air Conditioner Sizing | Heater Sizing
I am attaching the picture below.

So my question is why is such discrepancy. I am only comparing the highly hot and humid areas of USA with that of India. The ambient temperature in Arizona desert and Florida easily crosses 40 degree Celsius and sometimes go into 42-45 degree celsius.

I have a one ton inverter Hitachi AC installed [rated cooling capacity 12150Btu/Hr] for last 3 years in Cuttack, Odisha in a ground floor house with 144 sqft carpet area. It chills even if it is set at 25 degree celsius in a sunny day.

Now I am in Raipur, Chhattisgarh. Raipur is hot, but dry.

Just tell me why there is so much discrepancy. It can not be simply because of higher ambient temperature in India. I am comparing hot humid places like florida that require 1.5 ton for 600-900sqft area, and hot and dry area like arizona that also require the maximum cooling of 1.5 ton for an area of 600-900 sqft.

I have seen people setting the AC to 17 degree hoping it will chill faster. I believe they need only to set their AC at 25 degree to feel the chill. If outside ambient temperature is 40 degree C then any thing less than 30 degree will be cool as your body temperature is around 37 degree C.


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Any estimates about power consumption??
Like a 2star rated 1.5ton AC ?

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