Reduce the need for an active cooling system by improving the design of the dwelling. If the cooling load in Thermal Comfort is sufficiently low and it is realistic to have no cooling, then the highest-scoring option is "no cooling to be installed".
Depending on the local climatic conditions, ceiling fans or evaporative cooling may be appropriate and will score well.
If selecting an air-conditioner, choose one with a high Energy Efficiency Ratio (EER) or cooling star rating.
When choosing a cooling system, energy efficiency is one of the many factors that should be considered. Apart from initial cost, other considerations include maintenance costs, health and safety issues, reliability, noise, maintainability and life expectancy.