[observer53]

Originally Posted by MediocreButArrogant

That's not efficiency, that's capacity.



You seem to not understand that A/C units are sold with different cooling capacities, measured in tons, or BTUs per hour (one ton of cooling equals 12,000 BTU/hr). What you are suggesting is an oversized unit, which just about anyone in the business would say is bad. The problems with an oversized unit are:

1) Unit will cycle on and off too quickly, causing rapid temperature changes when unit runs. For comfort, the ideal situation is steady low flow of air that just keeps the house at the target temperature. That's why they sell multistage furnaces, so you don't get blasted by hot air when it isn't that cold outside and only a small amount of heating is needed. Multistage A/C is also available, though less common.

2) Unit will cycle on and off frequently, which means more starting and stopping of the compressor and blower motors. More start/stop cycles means earlier failure of the motors.

3) Since humidity is only removed when the unit runs, the oversized unit cannot remove as much humidity as the properly sized unit. Not an issue in this area, but in an area with high humidity, this is the most important reason to properly size a unit. An oversized unit will perform poorly at removing humidity and the homeowner will be dissatisfied with the system. This is also the reason for the more expensive multistage units; they can run with just one of the compressors at low settings for long periods of time, removing humidity without cooling the home too quickly.

I DO know they come in different sizes as you describe. I know that my system is not oversized. Beyond that, I claim no expertise in AC units whatsoever, so I'll bow out of this discussion.