Is a portable ac unit more energy efficient rather than using the central ac.?

Answer 1

The AC units themselves are generally less efficient than a central AC unit.

The minimum EER rating for a central AC unit is 10. The minimum for a window AC unit is between 8 and 9 depending on size.

Cooling Capacity ÷ EER = Watts.

Cooling capacity is rated in BTU/hr, where 1-ton equals 12,000 BTU/hr.

The savings for the consumer is when they only need to cool one or two rooms instead of the entire house. The cost per hour to run a window unit is substantially lower than a 3 to 5 ton central AC unit.

Answer 2

A central plant is almost always cheaper, if it's designed and operated correctly. Central systems can have water cooled units, which are significantly more efficient, and - since they usually have multiple units - can match their capacity to the load. So, instead of operating inefficiently most of the year (when loads are not at their peak), which a portable unit must do, the central plant would use a smaller number of units operating at a higher and more efficient load factor.

Typical numbers are 1.25 kW/ton for portable units and less than 1 kW/ton for a central plant (even an older one). Newer systems, with variable speed pumping and head pressure control get down to 0.5 - 0.6 kW/ton.

And, with a central plant, it becomes more feasible to install free cooling systems.

Answer 3

I would say that the obvious answer is yes. But thinking about it a little more will likely shed a little more information.

A portable unit is efficient at its designed area. Typically, central air is designed to operate at the entire area of the space. Since the portable will be strapped to maintain the temp setting nearing its maximum design area, the answer swaps to NO.

So the answer becomes relative to the direct efficiency of the cooling unit itself and NOT necessarily the size of the unit. Just because it is central does not indicate efficiency. So if you are STRICTLY speaking of efficiency then you need to look at each one individually for efficiency ratings and judge by that method. If you are just looking to see what will cool your house efficiently then having a small unit that runs 100% of the time at max capacity is surely not as efficient as a larger unit that is not under nearly the load.

Answer 4

If you need to cool a whole house, a central AC unit is much more effective and efficient.

I can cool 2500 sq.ft. with a 2 ton (24,000BTU) central air unit.

Answer 5

If your intention is to cool only 1 room, then yes. Otherwise they take more engergy to operate.