There is a factor which cannot be controlled, that being the load the unit is cooling or heating.
This load factor changes with things like humidity inside, humidity outside, the type of heat source inside (in AC mode), things as simple as whether or not the fireplace has a fire in it or not, etc.
IMO this is the reason the manufacturers are a little vague with their power numbers... as one can see; each structure is different, so the loads are different.
GA-HVAC-Tech
Your comfort, Your way, Everyday!
GA's basic rules of home heating and AC upgrades:
*Installation is more important than the brand of equipment
*The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
*The value of comfort, over the long term; leave economic choices behind!
Choose your contractor wisely!