The size of an air conditioner plays a far more significant role in its energy efficiency rating, as an air conditioner that is too small or too large for the space it is intended to cool will not operate efficiently.
An air conditioner that is too small for the space it is cooling will struggle to maintain a comfortable temperature, resulting in the machine constantly running, this can significantly reduce its energy efficiency. On the other hand, an air conditioner that is too large for the space it is cooling will cool the space too quickly and will short cycle, also reducing its energy efficiency.
In contrast, an air conditioner that is properly sized for the space it is cooling will run continuously, maintaining a comfortable temperature while using the least amount of energy possible.
While an energy star rating can be a useful indicator of an air conditioner's energy efficiency, it is important to consider the size of the unit in relation to the space it is intended to cool. A unit with a high energy star rating may not necessarily be the most energy efficient option if it is not properly sized for the space.
In conclusion, the size of an air conditioner is far more important than its energy star rating in terms of energy efficiency. It is essential to properly size an air conditioner for the space it is intended to cool in order to achieve optimal energy efficiency.